The document discusses the idiom "let the cat out of the bag", which means to disclose a secret. The origin of the phrase comes from the practice of substituting cats for pigs in markets. If the cat was let out of the bag, it revealed the trick and prevented people from buying a pig in a bag. The document provides three examples of using the idiom in sentences to reveal a secret that was meant to be kept private.

1. ANIMAL IDIOM 8

2. “ Let the cat out of the bag”