Used to describe cold weather, this saying derives from the traditional Navy phrase "cold enough to freeze the balls off a brass monkey". This references the brass structure or 'monkey' where cannon balls were stacked.

It was widely and incorrectly believed that the Beastie Boys were referring to a different drink made from a 40-ounce container of malt liquor mixed with orange juice ("forty" is mentioned in the lyrics); however, Mike D has publicly confirmed that the premixed Heublein cocktail was their inspiration.

There's no denying that the Beastie Boys were responsible for popularizing the Brass Monkey, but the origins of the drink are much more mysterious. In fact, the Brass Monkey they were rapping about was not orange juice and beer (or malt liquor), but a canned precursor to Smirnoff Ice.

The expression: "It is cold enough to freeze the balls of a brass monkey" comes from the practice of putting iron cannon balls on a dimpled brass plate on the deck of a war-ship. When very cold the brass contracted sufficiently to cause the iron balls to fall out.