Mine was derived from an inside joke amongst some of my online gaming buddies. I have since been slowly fading out my older online handle with this one.
The old handle was "Rraahk" in which I created by punching random keys on the keyboard (no line) and modifying the result to sound feline. I was naming a cat-person in Everquest at the time. I decided to retire it because it was too hard to pronounce (like "Rock") and spell (double r, double a) for most people.