Definition & Meaning of "[blow] the whistle on {sb/sth}"

What is the origin of the idiom "blow the whistle on someone or something" and when to use it?

The idiom "blow the whistle on someone or something" has its roots in sports and referee practices. In sports, referees use a whistle to signal a foul or violation. The phrase likely evolved from this practice, as "blowing the whistle" on someone or something means exposing wrongdoing or calling attention to improper behavior, just as a referee calls attention to rule violations during a game. This expression is used to describe the act of revealing or reporting unethical, illegal, or inappropriate activities, typically within an organization, institution, or group.