Well, I was around and on computers before the Internet and before The Sims (yes, children, there was still life before these things) and my username used to always be Bluejeans. As more and more people joined the online community, my name was harder and harder to secure.
Then, about 6 months after The Sims came out, I was invited to moderate one of the few fansite forums. I started writing tip columns, creating downloadable objects for the game, and moderating group discussions on the forums. In order to identify moderators on the board, we all changed our usernames to start with the letters LIU for Livin' It Up (the UK name for the first expansion pack of the first game)... hence, I became LIUBluejeans. And THAT username is never taken so I use it everywhere now.