Star Trek: 10 Things You Didn't Know About Dr Leonard 'Bones' McCoy

It's been assumed for ages that McCoy's nickname, Bones, was evolved from 'sawbones', a term that was used for military doctors in the American Civil War because of the saws that they used to perform amputations.

This was never stated outright in canon, and to complicate matters, the 2009 alternate universe film implied that the nickname's origin was something entirely different. Right after first meeting Kirk aboard the Starfleet recruit shuttle and complaining about the horrors of outer space, McCoy grumpily explained that he and his wife had just recently divorced, and said 'all I got left is my bones.' The camera then cut to Kirk, and it was pretty clear what was being implied.

J.J. Abrams explained in his DVD commentary of the film that this reveal was actually not scripted. Karl Urban was a Star Trek fan and thought the nickname could use an explanation, and thought of the line while filming.

Fans can debate which origin is canon to the prime timeline, but the term coming from the American Civil War seems much more realistic, given that many terms in Starfleet were borrowed from the United States military, and that Kirk in particular was a big American history buff. The explanation in Star Trek (2009) feels unnecessary and kind of silly, much like the origin story given to Han Solo's name in the Solo movie.