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.

"Cold enough to freeze the balls off (or on) a brass monkey" is a colloquial expression used by some English speakers to describe extremely cold weather.

The Brass Monkey is a cocktail made with dark rum, vodka and orange juice, sold as a premixed cocktail in the 1970's and 80's. It was sold by the Heublein Company, which later dissolved in 1998.

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.