'Bullet' is a fundamentally stupid first name for a person in an English-speaking environment.
How does someone get such a name?

(1) "Aw, what an adorable little baby son we've got! Let's call him 'Bullet', just in case he turns out to be a gunslinger."

(2) "Damn, man, I lost my hand. My name used to be 'Finger', but now I shoot bullets from the place my fingers used to be. Ah well, 'Bullet' it is then!


Actually, from the Dyne flashbacks, we know he's always had that name, so it wasn't something he adopted after the Corel massacre. 'Barret' at least is a name that an actual person might have. Descriptive names aren't usually that good, as with "Mash" Figaro in FFVI. Sabin, while an unusual and outdated name, has the benefit of being a real name.