Whistleblower
Etymology
The image is of blowing a whistle to stop play or raise an alarm — echoing a referee or a police officer. Consumer advocate Ralph Nader promoted the term in the early 1970s to replace pejoratives like “snitch” or “informer” with a word framing the act as public-spirited.
noun · /WISS-ul-bloh-er/
A person who exposes wrongdoing, illegality, or danger inside an organization to those who can act on it.
What it names
The insider who breaks ranks to reveal what an institution wants hidden, often at great personal cost.
Example
The whistleblower leaked internal memos showing the company knew its product was unsafe.
Related idea
A whistleblower reveals wrongdoing to protect the public; a leaker discloses information for any motive, and an informant typically works with authorities against peers, often for personal benefit.