I started using Baek a long time ago, taken from the character in Tekken 2. But since Hwoarang replaced Baek in Tekken 3, I felt I had to change my nick to Hwoarang.
After some time though, I realized how popular Tekken was on the net. Not only was the nickname used a lot at sites where you have to register, but you also ran into irritating people on IRC who wanted to ask me things like "DO YO LIKE TEKAN?"
And sometimes they simply wanted to tell me "I CAN CRUSH YUO WITH KING HAHA"
So yeah, I grew tired of all that, and I wanted to change my nickname yet again. I looked around for a nice nick to use, but I couldn't find anything suitable and original in the Tekken series anymore. So I glanced slightly sideways, and started going through other fighting games just to keep the tradition alive. I found Kilik from Soul Calibur, a nickname that's easy to remember and easy to write and read, both forward and backwards. And no, I'm not actually a big fan of Soul Calibur, I just happened to like the name.
I used it for a while, and realized it wasn't nearly as popular as Hwoarang (thank god). But people still used it here and there, and when I was about to register myself at GAF, Kilik didn't work. That's when I changed it to the romanized version of the name, so to speak. Kiriku, a nick I've been using for a number of years now. And I don't plan to change it for a while either.