Pat Shingeton: "Cold Enough to Freeze the...."
Early warships stacked cannon balls next to their guns. It was once believed that a method was devised to stack 30 balls in a squared "pyramid" configuration with 16 on the bottom and one on top. The design saved space and the movement of the ship rolled the balls over the deck and often - overboard. The solution was a metal plate called a "Monkey" that included 16 round indentations. To prevent the iron balls from rusting, the "Monkey" was unfortunately made of brass whereby brass contracts faster than iron in cold weather. When below freezing conditions occurred, the brass indentations shrunk and the iron cannonballs would lift off the "Monkey." Thus the expression... "its cold enough to freeze the (expletive deleted) off a Brass Monkey.