Well, it's a Spanish name, not from an indigenous language, so even though it's so strongly associated with an Apache with the name. The kids where I work might think of
Geronimo Stilton first.
http://en.wikipedia.org/wiki/Geronimo_Stilton I think I'd try to start calling him
Gerry/
Jerry. I'm sure I'd get used to it, even if he doesn't like the nn.