- The term "smoking gun" is a reference to an object or fact that serves as conclusive evidence of a crime or similar act, just short of being caught in flagrante delicto. (Wikipedia)
All sources appear to agree on the idea that the saying comes from a similar expression in a 1893 Sherlock Holmes story, The Gloria Scott, in which Arthur Conan Doyle wrote:
- 'The chaplain stood with a smoking pistol in his hand,'
Checking with Ngram the expression seems to have become popular only from the 70's, probably during the Watergate investigation:
- Nixon defenders insisted that while much impropriety could be observed, no proof of presidential obstruction of justice – 'no smoking gun' – had been found. (The Prase Finder)
Questions:
When did the expression actually become a set phrase? Was it 80 years after Conan Doyle story, or is its origin unrelated and only accidentally similar to the one used in the 1893 story? And if that is the case, where does the expression come from?
Best Answer
Christine Ammer, The Facts on File Dictionary of Clichés, second edition (2006) has this brief entry for smoking gun:
The use of "smoking gun" as a literal description of a gun with smoke rising from its muzzle goes back to at least 1843. From Alexander Marlinsky, Ammalát Bek, serialized in Blackwood's Edinburgh Magazine (June 1843):
The first Google Books match for "smoking gun" in a figurative sense comes from this rather amusing anecdote told (by an unidentified speaker) in American College Health Association, Proceedings of the Annual Meeting (1966) [combined snippets]:
As used by the speaker, a "smoking gun decision" is simply a decision made under extreme duress, as if while a smoking gun were being waved at you by the person asking you for your decision.
The first instance that Google Books finds of "smoking gun" in the sense of "irrefutable proof of guilt" appears in the context of the Watergate scandal of 1973–1974. The phrase "a smoking gun" or "the smoking gun" appears at least six times in Facts on File, Editorials on File, volume 5, part 2 (for the year 1974). And the earliest of these appears in an editorial from the [Cleveland, Ohio] Plain Dealer, (July 11, 1974):
I wouldn't be at all surprised to learn that lawyers in the United States (and elsewhere) have been using "smoking gun" in the figurative sense of "decisive proof" since long before Watergate. But the Google Books database yields no smoking-gun evidence of any such usage from before 1974.