At first I didn't want people to know what my in game user was, but there were only a few name themes I liked at the time. I pretty much refused to make a username that wasn't Realcottoncat, cottoncat, Lightning(Something about a cat), or Coyote(some animal body part).
So I smashed the first words of two of my spare accounts usernames together (Lightningmeow and Coyotewing). I then thought "Eh, this is nice enough to be called by on this site". If I had known this site was going to be my main social site for over a year and that I would have friends from it that still call me that around a year after I mostly quit this place, I probably would have used something else, but it worked out in the end because now I quite like it. A funny coincidence is that the way I pick usernames now-a-days actually ended up making this more in-keeping with my online personality than I thought it was at the time as it fits right in.