Star Trek: 10 Things You Didn't Know About Dr Leonard 'Bones' McCoy
9. McCoy Didn't Invent His Most Iconic Catchphrase
Don't get mistaken, Bones was a doctor and absolutely nothing else.
McCoy's iconic catchphrase, 'I'm a doctor, not a...', followed by literally any other job title, has been used by McCoy a staggering number of times. If you're interested in looking through all of the examples of this, there's a Memory Alpha page that compiled them all together. Among other things, McCoy is confirmed to not be a bricklayer, a physicist, a psychiatrist, a mechanic, an engineer, a coal miner, and an escalator.
This line has also been repeated by plenty of other characters throughout Trek, most frequently by Julian Bashir on Deep Space Nine and the holographic doctor from Voyager.
What's surprising is that 'I'm a (blank), not a (blank)' was even used years before McCoy was born, by Phlox (who was a physician, not an engineer), so McCoy himself clearly didn't invent the expression, though he certainly popularised it in Trek. It's the perfect way for folks in Starfleet to passive-aggressively tell their superiors that something is totally outside of their area of expertise.