"Cold enough to freeze the pawls of a brass monk's key".

Thanks for that, stales! My version pawls in comparison!

urban myth

Thanks, wofahulicodoc! The rebuttals are thorough and make a lot of sense. So does anyone have an inkling of the phrase's true entymological origins?...Uncle Tsuwm? help! Or, based on the brass monkey lineage of phraseology offered in this response, perhaps someone coined it who really was just talkin' dirty, after all!