A/N: For the sake of this fic, Kate has yet to call Rick, 'Babe'. Set in season 6, sometime after Pi has moved into the loft.

Disclaimer: I do not own Castle or the characters used in this story.

For (_MissKM_) who prompted me on twitter. Prompt will follow at the end.

Hypocorism

hypocorism (/haɪˈpɒkərɪzəm/; Greek - also known as a pet name or calling name,[2] is a shorter or diminutive form of a word or given name, for example, when used in more intimate situations as a nickname or term of endearment.

"This is ridiculous," Castle muttered as he stepped passed a fuming Kate, putting some distance between them so that they could cool off.

"No, you want to know what's ridiculous, Rick?" she argued, whirling around to face him, "that we can't even have a damn fight in privacy."

"What?" he asked, jaw squared and shoulders tensed from the ongoing fight they'd been having since they got up that morning.

"I'm a private person, you know that. I need my privacy and when I'm here, when we're here," she motioned to the room, indicating that she meant the loft, "there is absolutely no privacy."

His eyes widened as he finally realized what had been bothering her.

He'd woken up earlier than usual to find her already awake, and was even more thankful for it when the naughty grin on her face had him immediately rolling her under him. They were only about five minutes into their morning activity, just starting the build that delicious pleasure, when the loft's newest inhabitant, Pi, had barged into their room. It seemed that looking for yet another razor was far more important than knocking.

Castle had pulled the sheets higher over their naked bodies, made sure Kate was completely covered, but the embarrassment had already ruined the moment, and as soon as Castle had politely told Pi to get out, she had pushed away from him and ran into the bathroom, closing and locking the door behind her.

Ever since then she had been quiet, distant, brushed off any attempt of conversation that Castle tried to start. She snapped at him when he asked her about dinner and he had ignored it, but the final straw came when he had stepped up behind where she sat reading at the bar. The moment his arms wrapped around her and his lips had touched her neck, she pushed him away and stormed into the bedroom.

And before the real fight could even start, she could hear Pi and Alexis discussing what was wrong with her, because his damn room didn't have four regular walls.

"I'm sorry you feel that way," he finally answered, cutting through the awkward silence.

"I just—I can't do this, I can't handle not having anywhere to go for a private moment."

Now she was making him mad. "You knew that I didn't live alone when we got together, Kate. You never seemed to have a problem with it before."

"I don't have a problem with your family, Castle. I have a problem with the fact that we need some privacy and no one seems to respect that."

He seemed to soften a bit at her words, but when he stepped closer to her she backed away from him, causing to anger to flare to life once more.

"Seriously, you're not going to let me touch you?"

"No, not when every other person that lives here can hear everything we're doing and there's a chance that one of them could come barging in here again."

"I don't know what the hell you want me to do, Kate," he shot back, voice raised and anger dancing in the darkening blue of his eyes.

"What I want you to do is set some boundaries, some ground rules, something!"

"And if not then what? You're going to refuse to let me near you, go back to your apartment, fight with me about privacy every time someone interrupts us?"

His voice echoed through their room and no doubt through the rest of the loft as well.

"No, Babe, listen to me, please…We never –"

She stopped short when his laughter cut through her words, she wasn't sure what he found funny about this, but laughing was the last thing she wanted to do at the moment.

"Castle, what the hell is so funny? she asked, crossing her arms over her chest as he continued to laugh.

"I just never though the hard ass, no nonsense, Detective Beckett would use pet names," he answered once he had managed to get his laughter under control.

"What?" she questioned, shooting him a glare when he let out another chuckle.

"You just called me babe. You've never done that before and I just find it hilarious."

His amusement with her term of endearment only served to annoy her further and she rolled her eyes before walking away from him to sit on the edge of their bed.

"Kate?" he whispered, after she'd been quiet for a long time, but she only shook her head as he walked over to sit beside her on the bed.

"Don't, Castle. Just don't."

"Look, I'm sorry about there being no privacy, we'll figure something out, okay?"

She shook her head again but finally turned to look at him. "When we're at the precinct, there's no privacy. We can't even touch each other. And then we come here and we're surrounded by your family and I love them, Castle, I do, but when we come into our room we shouldn't have to worry about people barging in or hearing everything that we do."

She lowered her voice and leaned closer to him before she continued. "I'm sure it's no secret to anyone here that we have sex, but I'd really like to not worry about one of them seeing or hearing us when we're actually doing it."

He nodded his agreement and wrapped his arm around her shoulders, breathing a sigh of relief when she didn't push him away.

"I know, Kate. I'll talk to Pi and maybe a contractor?"

"Okay," she agreed, finally letting him lean in so that he could kiss her cheek.

"In the meantime, our bathroom door has a lock and I'd very much like to continue this morning's activities with you," he whispered in her ear, smiling when she shivered against him.

She let him pull her towards the bathroom, sighing in relief when he flipped the lock behind them and pinned her against it.

"By the way, you can call me babe anytime," he whispered, tugging on the waistband of her yoga pants.

"Really? You liked it? Because – "

He pressed his lips to hers, effectively cutting off her words.

"It just shocked me to hear you say it. But you know how much I like domestic Kate."

"Okay then, start the shower, Babe, I have plans for you."

Prompt: Kate calls Rick 'Babe' the first time during a big argument and Rick finds the idea of Kate using pet names funny, making the fight worse. He finds it hilarious because he never thought the bad ass Beckett would use mushy love names.

Would love to hear your thoughts! xo