It's a mix of "Rambo" and "bow", the "jo" is inspired by the antagonist from the powerpuffgirls, Mojojojo. I made this name up when I was 4 years old.
A random name generator called the Gamespy Naminator.
I use Jemma when playing online now. It's original I hear.
Does it annoy you when people spell your name Gemma??