Freezing Balls off Brass Monkeys
The origin of the expression "cold enough to freeze the balls off a brass monkey" is the subject of some controversy.
A British men's underwear company, Brass Monkeys, makes the popular claim that the term dates back to the British navy. Sailors were said to store cannonballs on brass platforms called "monkeys"; in cold weather, the brass would contract or break and the cannonballs would roll away free.
But websites dedicated to etymology dismiss this as poppycock. There is no historical reference to a "brass monkey" in any navy history, say the word police (although the boys who carried charges from the magazine to the guns were called "powder monkeys").
I post this article as it doesn't seem to provide any real relief for the question of the history of brass monkeys' balls and cold weather. Thus, if anyone needs a research project, please, feel free to pre-empt this one. I considered keeping this to myself for my own project, but I don't think I will have time in the near future, as I am still busy working on "sons of monkeys' uncles" and "water-tight asses of frogs" and the like.