Mine started as a pet name that my older brother's girlfriend used to call me by saying my first name really fast (the "th" in my name sounded like an "f"). I decided to use it as the name of my main character in an rpg, I think the game was Legend of Legaia but I'm not sure. Anyway, the name sort of stuck and it's my name for many things.
I don't know what else I'd call myself at all... It's been hanging around for a while
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-Jafin