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Idiom: Stool pigeon
Meaning: An informer; a member of a criminal conspiracy who trades information for his own freedom.
Example: “There’s a gentleman that’s going round, turning the joint upside down. Stool Pigeon – ha-cha-cha-cha” – Kid Creole and the Coconuts, “Stool Pigeon”
Origin: Everyone knows what a stool pigeon is, and everyone knows that it’s very bad to be one, but does anyone know what pigeons have to do with stools, or what either one has to do with confessing to the police?
There is a seemingly easy explanation in the practice, once common among hunters, of using a stuffed pigeon as a lure to attract other pigeons. There’s also the possibility that it derives from the French word “estale,” which refers to a decoy pigeon.
The problem with these theories, according online etymology site Phrase Finder, is that there’s no clear connection between the hunting practice and the metaphorical meaning of the phrase. “Stool pigeon,” with its current meaning, didn’t appear until the mid-19th Century in America, despite the long history of the practice of using decoy pigeons.
“The term ‘stool pigeon’, or ‘stoolie’, doesn’t appear in print until the 19th century and in a completely different context,” the Phrase Finder informs. “It is first used in American publications and referred to criminals who lured others into crime rather than to decoy birds.”
The best explanation, the site says, could be that stools refer to the barstools that such police informers would occupy in the seedy bars in which they mixed with the underworld.
Comparing an informant to a bird isn’t unusual, as informants are also referred to as “canaries.” Other colorful terms for stool pigeons are “rat,” “snitch,” “fink,” and, in the United Kingdom, “grass” (a Cockney rhyming slang term derived from “grasshopper,” which rhymes with “copper”).