Hunters in olden times tied a decoy pigeon to a stool in order to entice a hawk into a net, hence the expression stool pigeon. Today it is used more in the figurative sense for a person who works as a decoy or informer, especially for the police. The origin of the word pigeon lies in the Old French pijon, denoting a young bird, especially a dove; French borrowed it from the Old Latin pipion that means a ‘young cheeping bird’. In the USA, a gullible person, especially someone swindled in gambling or the victim of a confidence trick is called a pigeon.

In fact, pigeon has given many offshoots to language. In military slang, an aircraft from one’s own side is a pigeon. In the register of anatomy, a pigeon-breasted person has a projecting breastbone leading to a deformed chest and pigeon-toed is a person who has toes or feet turned inward.

A person with a responsibility to bear or entrusted with a particular business has a pigeon to bear, as in ‘the peace-talks are the pigeon of the Ministry for External Affairs’, obviously, not a job for a timid, cowardly or pigeon-hearted person. While letters for an official are placed in the allotted pigeonhole, an official who deals with confidential treaties can’t be pigeonholed as an ordinary government figure. This use of the pigeonhole can be traced to the original pigeonhole that was a small recess for a domestic pigeon to nest in.

A guinea pig has nothing to do with the guinea coin or the South African country Guinea. Neither is it a pig. It is actually a small rodent of the genus Cavia; used in earlier times for experimentation. The metaphoric sense is carried forward today when someone or something used as a subject of experimentation is called a guinea pig. Pig comes from the first element of the Old English picbred that is literally ‘pig bread’. Pig in the metaphoric sense figures in words like pig-headed for a stupidly obstinate person and pig-ignorant for an extremely stupid or crude person.