For some time now, some of my on-line friends have advised me to provide a version of CassidySlangScam without the invective aimed at Cassidy and his supporters. In response to that advice, I am working on providing a glossary of the terms in Cassidy’s ludicrous book How The Irish Invented Slang with a short, simple and business-like explanation of why Cassidy’s version is wrong.
A stool pigeon was originally a decoy, a pigeon attached to a stool or some other wooden structure used to lure other pigeons. There is some doubt about the real meaning of the stool element. Some people regard it as a corruption of a word stall which originally meant a decoy.
Its earliest occurrence is in this context, in a work of 1812 called History of Animals: Designed for the Instruction and Amusement of Persons of Both Sexes by Noah Webster:
In this manner, the decoy or stool pigeon is made to flutter, and a flock of pigeons may be called in their flight from a great distance.
It was not long before it acquired the meaning of spy or informer.
Daniel Cassidy, in his etymological hoax, How The Irish Invented Slang, decided that it really came from Irish, so he got a dictionary and set about trying to make up a ‘well-known phrase’ as a derivation. His first attempt, as published in the Linguistlist on July 24 2003, was stuail beidean [sic], ‘a storer of lies and calumny’, along with stoolie coming from stuailai [sic], a ‘storer of slander’. The word béideán is a dialect variant of béadán, which means gossip or slander. Cassidy used the alternative version because it sounds more like pigeon. Béadán is pronounced ‘bay-dahn’. Stuáil is a gaelicisation of the English verb to stow. Its main meaning is to pad, to pack or to stow.
By the time the book was published, he had invented another ‘Irish’ phrase, using the verb steall, which means spout. It can have the meaning tattle, but there is no evidence that anyone, anywhere, has ever used phrases like steall béideán in Irish to mean anything, let alone a police informer.