Mine is boring.

There I was, a teenager, staring at the battle.net login screen on Diablo 2, wanting to play online with some friends, but I needed an account so I could load up my sorceress and kill some minions of hell.

Everything I tried was taken, so I tried varying spellings and variations of different user names.

I finally found one that wasn't taken that I thought was "cool" in my teenage mind.

The name kind of stuck. I'm far too invested into this username now, I can't really change now without many months or years of reminding all my online friends who I am. I'm not angry with it, but I do think the name is a bit juvenile at this point.