cat out of the bag

The phrase "cat out of the bag" refers to a situation where a secret or hidden information is unintentionally or unexpectedly revealed or disclosed. It implies that whatever was concealed has been discovered or made known, often causing surprise, embarrassment, or consequences. The origin of this phrase is unclear, but one theory suggests that it may have originated from a medieval market scam, where a person purchasing a piglet in a bag would find a cat instead if they didn't inspect it properly before buying.