Some people give themselves names.
Other people have names given to them at there local poolhall and it sticks with them if they go pro.
Other people have names given to them by people who dont shoot pool and the name sticks.
Basically, the name can come from pretty much anywhere and usually has something to do with the person who is given the name or sounds good with there birth name.
Few of my favorite nick names to go with the pro names are:
Francisco "Django" Bustamante
Corey "The Prince of Pool" Deuel
Jennifer "Vendetta" Barretta
Johnny "The Scorpion" Archer
"Kid Delicious" Danny Basavich
Another one I liked is from a local player around here named Howard. People call him Howard the Duck, because of the movie and he was known for missing some ducks in pool.[/QUOT
It seems to me pool nicknames are earned by prominently good shooters....I mean, I always thought having a nickname kind of stamped a person or legitimized him as a really good pool player....yes, it would be lame for somebody to give himself a nickname...