Just about the last thing anyone would have guessed Beast Boy and Raven would have in common was a talent for learning languages. He spoke Swahili, French, and German. She spoke German, Latin, Romanian, Ancient Sumerian, Sanskrit, and Azaranian. They would spend quite a bit of time with each other, teaching one another the languages they knew.
French was easy enough to pick up for Raven, though Swahili was a far more difficult language to learn being very different from the languages she already knew. Meanwhile, Beast Boy picked up Latin and Romanian pretty decently, but Ancient Sumerian, Sanskrit, and especially Azaranian were brutal. Still, learning Swahili and Azarnian were the priority languages for them both to learn, so they could speak each other's native tongue.
Swahili was a language that had sounded like alien gibberish a few months ago, but now Raven could make out what Beast Boy was saying. The language flows very quickly, and for a beginner like her, a native speaker would frequently leave her in the dust, even now. Azarnian really was an alien language, however. There wasn't anything quite like it on Earth, or anywhere in this dimension in fact. It sounded almost like Latin, except far older and more mysterious. It suited her normal persona, and Beast Boy frequently felt like they were in a secret order of mages whenever they practiced.
It would be a lie, however, if they said they simply wanted to learn the languages for the sake of learning them. Titans Tower was home, but it was also a home where absolute privacy tended to be rarer more often than not. Learning each other's languages would be a way to circumvent that, and let them talk about whatever they wanted in earshot of any of their friends. They would be curious, and the frequent blushing meant that they could put two and two together very easily. But, unless Starfire ever kissed them, they would never have to worry about Cyborg hearing them talk how they needed a sturdier bed, or how to get protection without causing a scandal in the tabloids.
It seemed to work when they spoke in German. Then Robin had asked them to never talk like "that" to each other in front of him again. French ended up being a no go too when Starfire told them she learned it from Robin too. So, they ended up going for broke and started teaching each other the most obscure language they knew. The first, successful test run was when they talked in-depth about a new movie, heavily spoiling plot details while the others looked on in confusion.
There was something nice about this kind of privacy. Being able to talk about anything, while their friends could any hope they weren't talking about a night together. It was a desire for more privacy that ended with them spending even more time together and learning about one another. They had an even stronger relationship now, and it was all based on the desire to be able to say "I want to take you to bed now" in front of Cyborg.