Cat’s out of the bag

The slang term “cat’s out of the bag” means that a secret or hidden information has been revealed or discovered, and there is no way to keep it hidden anymore.

This phrase originated from the practice of dishonest market sellers who would deceive customers by substituting cats for the more valuable pigs or rabbits they were selling. Once the buyer realized the deception, the cat would literally be out of the bag, exposing the trickery.

Examples:
1. “I accidentally mentioned the surprise party in front of her. Well, the cat’s out of the bag now!”
2. “He thought he could keep his job offer a secret, but when his coworkers overheard his phone conversation, the cat was out of the bag.”