How and why did you choose your username?

Well, my username was actually made up, a friend of mine who always called me "Mattish" and I called him "Gunnish" we are both born 1991 and yea that's pretty much it, we got an invite from our teacher to gmail back in 2005 and apparently "[email protected]" was taken so added .91 to it and that was it, I got it everywhere nowadays since it was way back and why change something that is not broken ^^