Regarding the phrase “Cold enough to freeze the balls off a brass monkey.”
I have been told that a brass monkey is (was) a contraption used on a sailing ship to hold the cannon balls. Brass, so as not to create sparks which might set off an explosion. In extremely cold weather the contraction of the brass woud allow the contraption to come apart and drop some of the cannon balls. So this really has nothing to do with a primate.
LINK TO COLUMN: Is it possible to freeze your cojones off? - The Straight Dope
Folk etymologies, while fun don’t really teach us anything useful.
Welcome to the Straight Dope Message Boards, lstrclmn, we’re glad to have you here. When you start a thread, it’s helpful to other readers to provide a link to the column you’re talking about. Helps keep us on the same page and saves searching time. No biggie, I’ve added a link to your post, and you’ll know for next time. And, as I say, welcome!
Here’s the last thread where the cannonball-holder theory is discussed further …
Can’t this article get an update, to cover the false folk etymology about cannon balls?