First name + high school nickname.
I played ion the soccer team at a predominantly Hispanic school, but because I was stupid I took German my freshman year. Every time someone spoke to me in Spanish, I replied "queso" because I was 13 and I somehow found this response to be hilarious. My teammates eventually didn't hate me but continued to call me Queso. I had a few soccer teammates on the basketball and football teams with me too, so the nickname came with me and spread to other, non-soccer teammates.
The combination is unique enough that it's an available username on every platform, with the exception of Twitter (fuck you Brian Que in California!).