The episode that now has President Donald Trump staring down a House impeachment inquiry began, as many important moments in American history have, with a whistle-blower.

A U.S. intelligence official has accused Trump of urging Ukrainian President Volodymyr Zelensky to seek out evidence of wrongdoing on the part of former Vice President Joe Biden, the frontrunner to face Trump in the 2020 presidential election. The claim relates to calls that took place in July and August, and the Inspector General of the Intelligence Community Michael Atkinson alerted House Intelligence Committee chair Adam Schiff about the complaint on Sept. 9.

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America’s history with whistle-blowers is as old as the country itself, but the popular idea that they are courageous hasn’t meant whistle-blowing isn’t still risky, says Tom Mueller, author of Crisis of Conscience: Whistleblowing in an Age of Fraud, out Oct. 1. And in the intelligence community, where sharing secrets is a loaded idea, whistle-blowing is even more complicated.

The origins of the term “whistle-blower” are murky — one theory holds that it’s a reference to the whistle blown by British policemen when they saw foul play, and another says it’s a sports reference to the whistles blown by referees — but the principle dates back to medieval England by way of Roman law. Central to the existence of whistle-blowers is the concept that sometimes individuals, not governments or law-enforcement, need to be the ones who raise the alarm about wrongdoing.

At a time when there was no national police force, people who noticed transgressions could report them to the King’s representatives, under what was known as the qui tam provision. (That name comes from the phrase Qui tam pro domino rege quam pro se ipso in hac parte sequitur, meaning “He who sues on behalf of our Lord the King and on his own behalf.”) To incentivize this kind of whistle-blowing, and in recognition of the negative social consequences that might come with it, the government made it a lucrative proposition: if a conviction followed, the person who did the reporting got some of the bounty. The earliest known example of the application of qui tam is King Wihtred of Kent’s 695 declaration: “If a freeman works during the forbidden time [i.e., the Sabbath], he shall forfeit his healsfang [i.e., pay a fine in lieu of imprisonment], and the man who informs against him shall have half the fine, and [the profits arising from] the labor.”