Most of us know that “letting the cat out of the bag” means to reveal a secret. But how did this term come about. It seems that there was an old scam of selling young piglets in a bag and substituting a cat for the piglet, thus taking the buyer’s money who in turn would get a cat (and probably a feral one at that). If the cat was let out of the bag before the deal was closed, the scam would be revealed and the seller out any money.