It sounds really cringy, but it has an intresting backstory.
So osu was kind of the first game i have began actively playing. I have started playing it when i was 6 years old, and since you can't rename yourself it stays like that.
Basically i wasn't very original and didn't think too much of it because i have wanted to quickly play, and i have just reversed my name (nikita) and put my date of birth. It sounds like a joke and like the worst username ever, but it reminds me of myself as a kid and i really like it because of that. I would have changed it, but maybe it will stay for good.
During the big Dubstep trend about 7-9 years ago, there was a very popular artist named "SKisM". His music was one of the best next to Flux Pavilion and Skrillex.
My username before that was "LoLMeCrazy" so I definitely needed a new ign, so I went with "SKiisM" since I was a huge fan of his music. Barely anyone recognizes the name since the artist phased out awhile ago too.
My username comes from my DevianArt account, but I don't remember how did I get the idea.
I just remember that it was a different username but it was already taken so I said: "Let's just change a few things".
And it end up being Niktushi. lol
My friends gave me the nickname "Rappe" on 1st grade and then I turned it into Rabbe and now it's Rabbecito just for the memes. Mostly I use Rabbe on other platforms like Discord etc.