A/N: What? Another upload so soon? I know, I'm shocked, too XD
I actually wrote the majority of this a few months ago, but I randomly finished it today XD

Established Ace!Sherlock/John: John calls Sherlock by a pet name, so Sherlock decides to reciprocate. It is harder than he expects XD But he gets some help from an unexpected source ;-D

You might consider it to be like a sequel to 'Improbability', but it probably makes sense on its own XD

Thank you for reading, and please tell me what you think! ^_^

Sherlock sat at his microscope, attention completely focused on the sample of tissue in the slide. After such a refreshing night of sleep, he had got quite a lot of work done. Perhaps he might sleep a bit more often.

But only if John would sleep beside him.

Just as Sherlock was mentally reproaching himself for such a thought, he heard John's tread on the stairs. He glanced at his watch; it was a quarter to six, John was later than usual. His gait was perhaps slower than normal. He must have been to the shops then, Sherlock thought.

'Hey,' John said as he came into the kitchen. 'I'm home.'

'Obviously.' Sherlock suppressed a wry smile, but didn't look up from the microscope.

John sighed a little, putting the shopping on the counter. 'Have you been there all day?'

'Of course not. This morning I solved a cold case for Lestrade, and I was sitting on the sofa.'

John shook his head with a laugh.

'You're impossible. I'm gonna make spaghetti for dinner, and you're going to eat it.'

'Hm.'

'Did you even eat at all today?'

'Hm.'

John sighed again.

'At least have some tea.'

Sherlock finally tore his gaze away from his experiment. 'Fine. But then I'm going back to my experiment.'

'After dinner.' John always made tea the exact same way, yet somehow Sherlock never got bored of watching him do it.

'Before dinner. After I've had tea.'

'All right, but then after dinner you have to wash the dishes.'

The dishes. How Sherlock loathed that… that inconvenience.

'Or…' John started, but trailed off, obviously hoping to pique Sherlock's curiosity. (It usually worked.)

'Or…?'

'Or, after dinner, you could watch a film with me, instead of working on your, er. Experiment.'

Sherlock weighed this option. Watching a film would be dull… but if he did, then he and John would be sitting on the sofa. Together. The chances of it turning from just sitting into having a cuddle were high. Sherlock couldn't ignore statistics like that.

Besides, he did not want to wash the dishes.

He made a big show of annoyance, though he suspected that John knew what he was actually thinking. 'All right, I'll watch your film. But if my experiment is ruined…'

John held up a hand to stop him. 'If your experiment is ruined, I'll personally go and get you some new samples. Is that fair?'

Possibly Sherlock's bottom lip was protruding more than was actually necessary.

'I suppose it is. Thank you for being reasonable.' (John had once told him that if you thank people, it's easier to get what you want. Not in so many words, of course, but that had been the essence of it. So sometimes Sherlock would employ this method, if he thought it would help, and so far, results had been favourable. Well. Except the time when he had thanked Anderson for being stupid. Lestrade had been rather angry.) John made an odd choking sound in his throat and turned away. Sherlock made a mental note to get something when next he went out for that cough John seemed to be getting.

John finished making the tea.

'Here you are, love,' he said as he handed a mug to Sherlock.

What fortunate timing, Sherlock thought. He had been looking to address that, but was uncertain as to how to approach it. John had saved him some work.

'Why do you call me that?' he asked as John sat down.

'What?'

Sherlock was certain that John knew exactly to what he was referring; but then he thought that perhaps John hadn't really been paying attention to what he was saying because his mind was otherwise occupied (he did this often), and so decided to repeat himself. But only this once, of course.

'Just now you called me "love". And last night, as well. Why?'

John stared at him, looking like he was trying to determine how serious Sherlock was. It made Sherlock wonder whether it was an inappropriate question, though his latest internet research had indicated that in an intimate relationship, there must be open communication, and that it is all right to ask one's partner things which one cannot ask anyone else. And Sherlock was positive that his relationship with John could be called 'intimate'. But perhaps… he was wrong?

'Well, I,' John said, pulling Sherlock away from his thoughts. 'Do you not like it? I won't do that if it bothers you.'

That didn't exactly answer his question, but Sherlock was momentarily distracted. Did he like it?

He didn't… mind. It wasn't annoying or unpleasant. When John had first called him that, it had been surprising, but then he had berated himself for not realising that, of course John likes to call his partner by a term of endearment- just look at his shoes. It was quite obvious.

And when he'd said it, it had just seemed very… natural. Not forced or insincere. As though John had always called Sherlock 'love', since the day they met. In fact, it had been rather nice. Perhaps Sherlock could get used to that.

'No, it's- fine. It doesn't bother me. I only want to know why.'

'Why?

'Ah good, you can hear.'

John rolled his eyes at the sarcasm, but his look softened as he said, 'It's just… how you show your affection for someone, that's all. You know, like you want to let them know how important they are. To you.'

'Interesting.'

Now John frowned at him. 'What, hasn't anyone ever called you by a name like that?'

Sherlock let his thoughts drift far away for a bit. 'My mother did.' After a moment or two, though, he began to scowl. 'And Mycroft used to call me "dear", as if he were so much older than me, and he thought he was my father or something.'

'I don't think he meant it like that,' John said with a laugh.

'I am certain he did.'

'He's your brother.'

'I would prefer for him to act like it, instead of trying to be my—parent.'

'I know, darling. But it's only because he cares for you.'

'Hm,' was Sherlock's distracted reply, because he was already thinking about something else:

Darling. That was different than before. Was there some sort of significance in what name John chose to call him?

Sherlock's face must've reflected his thoughts, because John was chuckling a bit.

'Do you not like that one, then?'

Sherlock put his hands together, thinking. Dislike it- no. It was different than 'love' but he supposed the feelings behind it must be the same, or at least similar. Obviously it was not insult. So he reasoned that as long as the feeling remained the same, it wouldn't really matter what word John used.

'Call me whatever you like,' Sherlock said decisively. 'But- not when we're at a crime scene, or in front of Mycroft. Please.'

John made that choking sound again (and Sherlock added 'soon' to the aforementioned mental note). 'Right. Definitely not.'

They sat in companionable silence for a few minutes. Then something occurred to Sherlock.

'John.'

'Hm?'

'Am I to call you by a term of endearment as well?'

'Only if you want to. Because if you don't want to, and it doesn't- come from the heart, then it's rather meaningless, don't you think?'

How interesting. Sherlock had never actually used a term of endearment with anyone, except for when he was small and would call Mycroft 'brother', which he usually only did now to irritate him, tacking on a sarcastic 'dear'. (Irritating Mycroft has always been alarmingly easy and almost unfailingly entertaining. Mycroft often retaliated by calling him 'little brother', but it never did have the same effect.) However, Sherlock certainly did not want John to think that he had less affection for John than John had for him. He was almost sure that John wouldn't think that, but then again, sometimes emotion could get the better of one's logic.

But if he were to call John something, then what? And when? He tried to picture it in his mind. He suddenly had a vision of himself leaving the flat, saying to John, 'I'm off to the morgue to get some severed toes, darling.' That was… disturbing, frankly.

'I will get back to you on that, John,' Sherlock finally said. He would need to do more research first. Preferably after John went to bed.

The rest of the evening was pleasant; Sherlock did indeed eat some spaghetti, and sat through almost the entire film, even though it was dull. John tried a myriad of other endearments, much to Sherlock's amusement. He started with 'pass me that, love', and then, 'I'm gonna make tea, do you want some, beloved?' He teased: 'What do you think of this film, dear? Shall we watch another, gorgeous?'

Really Sherlock was kind of appalled that John had so many ridiculous things to call him. He went through 'mate', 'teacake', 'sugar cane', 'honeybee', 'snapdragon', 'china doll', 'my blue-eyed darling'. How on earth could he think of them? The face Sherlock made at 'muffin' must have clearly communicated his thoughts, because John about died for laughing and promised to stop.

At eleven, John wanted to go to bed. He was a bit disappointed when Sherlock said that he wasn't tired yet. Sherlock didn't want to upset him, really he didn't, but he needed to think and do some research.

'I just have something to take care of. I'll possibly join you later.'

'All right,' John said, leaning over to kiss him. 'Good night, sweetheart.'

Sherlock felt heat flood into his face and knew he must be blushing, but he couldn't help it.

'Oh? You like that one, do you?' John asked, grinning.

'No—I was only—surprised,' Sherlock, embarrassingly, didn't know what to say. Because the truth was that he liked it very much, indeed- too much, perhaps.

'You're so cute,' John teased, pinching Sherlock's cheek jokingly.

Sherlock, scandalised, stared up at him, 'Cute? What!'

But John only laughed and went to bed.

'Well!' Sherlock huffed to the empty room. The skull sneered back mockingly. 'Shut up, no one asked for your opinion.'

The skull, not one to learn a lesson, continued to smirk silently. But then, Sherlock wasn't one to let the derision of others stop him when he was on a case, and this was as much a case as anything else.

He turned on John's laptop, easily cracking John's most recent password ("Baskerville"? Really, John? Sherlock loved him, but John could be very… uninspired, sometimes) and went to the various dating and relationship information web sites.

He was a little discouraged, though. There were thousands of suggestions for pet names, but they weren't very… good. Some were too clichéd to even consider, while others were downright strange.What on earth was a "pooky pooky"? "Romeo" seemed too ill-fated for Sherlock's taste, and he highly doubted that "doobie" was an actual word. The lists went on and on and Sherlock still found nothing, so he decided to take a different approach.

Instead of searching for pet names, he looked for how to come up with one on his own. The Internet suggested to take one of John's qualities and then add to that some typical endearment or another.

Fine, then. John wore jumpers all the time, and that was adorable (not that Sherlock would ever tell him so) So… "jumper… dear"? No. "Darling jumper?" No, no. "Jumper eyes"? That… didn't even make any sense.

Sherlock sighed to himself. This was much harder than he thought it would be.

Perhaps a different quality then? Blue eyes… short… ears—what? No, that was—terrible.

He was going about this all wrong. He needed to think.

Normally, Sherlock would play his violin to help him think, but John was asleep.

Not that he wasn't playing his violin because it would wake John—what did Sherlock care? He could play his violin whenever he liked, whether John was asleep or not.

He just didn't like to play right now.

He went to the site Youtube and searched for opera videos (John had showed him the site, but was always showing him videos of cats. Why would he look at cats when there were videos of fantastic opera productions available? John was so strange sometimes!). He'd always been particularly fond of 'Le Nozze di Figaro' (well, and of Mozart in general) and since there were a few complete productions uploaded, he thought it wouldn't be amiss to watch one. 'Le Nozze' has romance as well as humour, after all, so it seemed appropriate.

Sherlock, having loved music for as long as he could remember, was soon carried away by the opera. The production's Susanna was brilliant and he found himself somewhat in love with her voice. In other words, he became completely and utterly distracted. Halfway through 'Aprite un po' quegli occhi', though, he realised that it was getting quite late and that he still had to think of a pet name for John. Oh, but Susanna's voice! He had to hear her 'Deh vieni non tardar'. He secretly adored that particular aria, finding it very romantic, and he couldn't very well sleep without hearing it! It was only a few minutes, and he could spare a few minutes.

So he sat enraptured, mouthing the words he knew by heart along with the singer, whose sublime voice allowed him to float off with romantic fancy for a little while.

And, as anyone might know, floating off with romantic fancy is a very good way to come up with romantic ideas.

There! How simple! Sherlock was almost angry with himself for not thinking of it earlier.
Not bothering to turn John's laptop off properly, Sherlock hurried to his room, bounding onto the bed and waking John up before he could think better of it.

'Hey—what?' John sat up, looking confused. 'Are you—all right?'

'Yes—better, actually, since now I've thought of it!'

'Thought of what?' John looked confused and very sleepy.

'Did you forget already?'

'Well, I was asleep.'

'Oh. Right,' Sherlock frowned to himself and looked away for a moment, thinking. 'Well, anyway,' he continued, shaking his thoughts off, 'I've thought of what I might call you.'

John had to smile then. 'All right. What is it?'

'Well, it's—wait!'

'What?'

'No, I've done it wrong. I'm supposed to just say it naturally, the way you did. Quick, tell me "good night".'

'Good night?'

'No, no, like you did before!'

John's eyes, discernible in the darkness of the bedroom, looked nearly black, but still Sherlock could see when the understanding lit them.

'All right. Lie down first.'

'Oh, fine,' Sherlock huffed, still trying to not be tired. He lay down beside John, facing him. 'Go on, then.'

'Patience.' John leaned down and kissed Sherlock on the forehead before lying down, himself. 'Good night, sweetheart.'

If Sherlock blushed again, John couldn't see it.

'Good night, tesorino.'

'W…what?'

'Tesorino. It means "little treasure".'

'Little-!'

'What? It's affectionate, and you are short.'

'I am not that short!'

'You're shorter than me. And again, it is affectionate.'

'Oh! Fine! Fine. But if you ever call me that in front of anyone—'

'I won't,' Sherlock laughed. 'I only like to upset you sometimes, ben mio.'

'Shit, you're not gonna get all pet-name happy, are you?' John complained, clasping his arms around Sherlock's neck.

'I have no idea what that means. I'll just say "no".'

'Good. You'd better not. Anyway, I'll get you for this. You're washing the dishes tomorrow, mister.'

'What!'

'Good night, Sherlock.'

'Good night, John.'

John didn't need to see him to know that Sherlock was smiling.