I don't know either. I took over an account on W16, didn't want people to think I was using an alias when I posted to hide, and had multiple accounts on other worlds like 24 and 36. So to solve the problem, I made a new forum username (the in-game account was u6s5l, without the ., and he couldn't remember his forum password), and stuck with it. I still have no idea what it means, where it's from, or anything really.