What part?

Try telling a jeweler over the phone that this part of your watch has snapped off, when you don't know what to call it.

"Buckle Tongue" on Strap...

See what I mean? One person saying it's called "buckle tongue," and another calling it "prong" I've also heard it called "pin" and "jabby thing." People have all kinds of names for it.

prong (that's a single prong buckle.)