guinea pig [M17th] The guinea pig comes from South America—not Guinea in Africa, or New Guinea in the South Pacific. Guinea pigs are chubby and can squeal like pigs, but why guinea was chosen nobody is really sure. The word could have been confused with Guyana, which is in South America, or was possibly used as an example of a far-off, exotic country that no one knew much about. Guinea pigs have been bred by humans for some 3 000 years, and are no longer found in the wild. Their use in animal testing led to the word’s acquiring the sense ‘a person or thing used as a subject for experiment’ in the 1920s.