Everyone “knows” that this is a bit of nautical slang dating back to the age of sail. A loose cannon careening about on the deck of ship could be quite dangerous. But while the metaphor behind this phrase is undoubtedly nautical, it is a rather modern formulation and has not been found to have been in use among sailors.
The metaphor first appears in Victor Hugo’s 1874 novel Ninety Three. Chapters four and five of that novel feature a loose cannon being tossed about the deck of a ship. Here is part of the incident (in translation from the original French):
The carronade, hurled forward by the pitching, dashed into this knot of men, and crushed four at the first blow; then, flung back and shot out anew by the rolling, it cut in two a fifth poor fellow [...] The enormous cannon was left alone. She was given up to herself. She was her own mistress, and mistress of the vessel. She could do what she willed with both. [...] The cannon came and went along the deck. One might have fancied it the living chariot of the Apocalypse.
Hugo’s novel was quickly translated and widely read, as evidenced by this 1875 quotation from Henry Kingsley’s Number Seventeen:
At once, of course, the ship was in the trough of the sea, a more fearfully dangerous engine of destruction than Mr. Victor Hugo’s celebrated loose cannon.
The phrase first appears without direct reference to the Hugo novel, as metaphor in a political, not nautical, context at the end of the 19th century. From the Galveston Daily News (Texas), 19 December 1889:
It would in no event become, as Mr. Grady once said, “a loose cannon in a storm-tossed ship,” for the very reason that it has not intelligence enough to voluntarily stand alone as a class and vote as a political unit.
While citations can be found for loose cannon dating back to the 19th century, the term did not become commonly used until the latter half of the 20th century.
It is claimed that Theodore Roosevelt popularized the term in a 1901 statement, where he said, “I don’t want to be the old cannon loose on the deck in the storm.” But this statement is not reported until 1946 and it’s uncertain how accurate it is.
Copyright 1997-2017, by David Wilton