Lloyd Sponenburgh writes:
I know this trivia ... but most don't.

That's what you think.

WHAT does it mean to "freeze the balls off a brass monkey"?

The answer is that if this phrase ever referred to anything specific,
it's no longer known for sure.

Larry Green answers:
I grew up in the UK and at one time it was very common to see 'brass
monkeys' sitting either on the mantelpieces above a fireplace or in the
hearth ... 'See No Evil' ... 'Hear No Evil' ... and ... 'Speak No Evil'.
In very cold weather ... if the monkeys were to stand up they could
have left their testicles behind.

This is as good an explanation as any -- simple hyperbole.

Lloyd now comments:
Nope. But it does have something to do with balls. G

Lloyd needs to read these references:

http://www.worldwidewords.org/qa/qa-bra1.htm
http://www.snopes.com/language/stories/brass.htm
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