blow the gaff

"Blow the gaff" is a phrase, typically of British origin, that means to expose a secret or reveal something that was meant to be kept hidden. It refers to a situation where someone unintentionally or intentionally discloses confidential information, bringing an end to secrecy or deception. The phrase can be used in various contexts, such as revealing a hidden agenda, exposing a dishonesty, or divulging classified information.