Hmmm, let me think about mine. My parents chose it, and I didn’t have much choice in the matter.
My normal go-to screen name though is Dabrainbox; I was a smart kid so I got nicknamed “brain box” by a lot of the other kids at my school, when I first got on the internet and had to pick a username I tried TheBrainBox, but a lot of places have 10 character limits on usernames. I shortened “The” to “Da”, which also gave it a more informal tone, and it’s stuck ever since across multiple platforms.
I used to go by that in the Open Legend community as well, but when I got involved with the moderator team and helping to develop the system I decided that I was proud to have my real name associated with OL, and so I changed it