Let the cat out of the bag
English Idiom
Meaning: To reveal a secret or disclose information that was meant to be kept confidential. It often happens unintentionally, causing surprise or sometimes even trouble.
Origin: The phrase 'Let the cat out of the bag' dates back to the 18th century. It originated from market vendors who would deceive buyers by substituting a cat for a piglet in a sack. When the buyer opened the bag, the cat would be revealed, exposing the trickery.
