Someone brought this article into my office this week ... it gives the history on some of the funny sayings we Americans have. Thought I'd share a few of them ... the entire article is pretty cool
Letting the cat out of the bag: In the Middle Ages, if you weren’t careful, it was said, an unscrupulous grocer might cheat you out of the suckling pig you’d purchased for a special dinner. While your back was turned, he’d instead slip a stray cat into your shopping bag. When you returned home and unloaded your groceries, you’d discover an unpleasant secret—by letting a (very angry) cat out of your bag.
Caught red-handed: Several hilarious but incorrect explanations exist for this expression, from references to thief-deterring dye bags in bundles of money to an outrageous legend about lower classes being forbidden to eat pistachios. “The intellect is our means of making sense of things,” Doyle says. “If we can’t discover sense, we will fabricate it.” In truth, “caught red-handed” refers to criminals who were apprehended while they literally still had the blood of their victims on their hands.
Mad as a hatter: These days, we expect nervous breakdowns from celebrities, but oddly enough, the cliché once applied specifically to hat makers. Mercury was once used to treat felt, so a disproportionate number of milliners, who worked for years on end with the poisonous substance, ended up in mental institutions with neurological damage. The expression became even more widespread after author Lewis Carroll used it as inspiration for a character in Alice in Wonderland.
Raining cats and dogs: Unfortunately, the story behind this popular expression is far from warm and fuzzy. Back in 17th-century England, poorly designed gutter systems sometimes caused stray dogs and cats to drown during major downpours. After a storm, it wasn’t uncommon to see the dead animals in the street, which, Evins says, “led some people to conclude they had actually come from the sky,” like the rain.