Cold Enough to Freeze the Balls Off a Brass Monkey

The persistent explanation claims that Royal Navy warships stacked cannonballs in pyramids on a brass tray called a "monkey," and that in freezing weather the brass would contract faster than the iron cannonballs, causing them to fall off, hence cold enough to "freeze the balls off a brass monkey." It's a wonderfully specific piece of naval engineering trivia. It's also almost certainly false. No such brass cannonball trays have ever turned up among the Royal Navy's extensively preserved historical equipment, contemporary records show cannonballs were actually stored in wooden racks called "shot garlands," and the real difference in how brass and iron contract in the cold isn't anywhere near large enough to make the story work physically. Some etymologists believe the "cannonball tray" explanation is a relatively recent invention, possibly from as late as the 1980s. Earlier versions of the joke about a "brass monkey" losing its tail, nose, or whiskers to the cold suggest the phrase was always a flexible, rhetorical exaggeration rather than a literal reference to any specific naval object.