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.
The phrase cold enough to freeze the ball off a brass monkey is a well known by English speakers.
It is an English phrase, but we don't know if it is a well known one.