From Naval History & Heritage Command:
It has often been claimed that the "brass monkey" was a holder or storage rack in which cannon balls (or shot) were stacked on a ship. Supposedly when the "monkey" with its stack of cannon ball became cold, the contraction of iron cannon balls led to the balls falling through or off of the "monkey." This explanation appears to be a legend of the sea without historical justification. In actuality, ready service shot was kept on the gun or spar decks in shot racks (also known as shot garlands in the Royal Navy) which consisted of longitudinal wooden planks with holes bored into them, into which round shot (cannon balls) were inserted for ready use by the gun crew. These shot racks or garlands are discussed in: Longridge, C. Nepean. The Anatomy of Nelson's Ships. (Annapolis MD: Naval Institute Press, 1981): 64. A top view of shot garlands on the upper deck of a ship-of-the-line is depicted in The Visual Dictionary of Ships and Sailing. New York: Dorling Kindersley, 1991): 17.
From Wikipedia, the free encyclopedia
This article is about the colloquial expression. For other uses of the term, see Brass monkey (disambiguation).
The phrase "cold enough to freeze the balls off (or on) a brass monkey" is a colloquial expression used by some English speakers. The reference to the testes (as the term balls is commonly understood to mean) of the brass monkey appears to be a 20th-century variant on the expression, prefigured by a range of references to other body parts, especially the nose and tail.
During the 19th and 20th centuries, small monkeys cast from the alloy brass were very common tourist souvenirs from China and Japan. They usually, but not always, came in a set of three representing the Three Wise Monkeys carved in wood above the Shrine of Toshogu in Nikko, Japan. These monkeys were often cast with all three in a single piece. In other sets they were made singly. Although three was the usual number, some sets of monkeys added a fourth, with its hand covering its genitals. Old brass monkeys of this type are collectors' items.[1][2] Michael Quinion, advisor to The Oxford English Dictionary and author of World Wide Words says "It’s more than likely the term came from them".[3]