Interesting that the phrase was never said, but that's what James Doohan named his autobiography.
By the way, James was shot 6 times during WWII. He lost the middle finger of his right hand to one of those shots. Like Gary Burghoff in M*A*S*H, whose deformed left hand was cleverly hidden throughout the series (except for a few times when it could be seen), James hid his right hand, although it can be seen occasionally if you're looking for it.
He also lost his Scottish accent in The Doomsday Machine (the one with William Wisdom). Scotty has rigged Wisdom's ship to blow up and is showing Kirk what to do. He says something like, "Just push this button and 'boom'." No accent.
By the way, I loved his performance on TNG's 'Relics'. The scene in which the holodeck doors open to the Empty enterprise bridge is actually lifted from the original series episode 'This Side of Paradise'. Kirk is the only person aboard the Enterprise and a brief shot of the empty bridge is shown before the turbolift doors open and Kirk steps through. That short clip was looped for that scene in 'Relics'.