The origin of the term "guinea pig" is uncertain. It perhaps comes from English speakers using the location Guinea to mean a vague, foreign land and the animal's resemblance to small pigs. Guinea pigs are native to the Andes and not from any location named Guinea past or present.
The word "guinea" came into English from Portuguese. Guiné was what Portuguese explorers called the area in West Africa that is south of the Senegal River. English speakers first encountering the animal may have been confused as to its actual origins. A similar confusion resulted in another domesticated American animal, the turkey, being named after a location in Eurasia. Another theory on the term is that the animals were first transported to English-speaking lands via ships called guinea-men, vessels which plied the triangle trade between Africa, the Americas and Europe. The word "guinea" is also similar to "Guyana", which actually is a location in South America. However, it is nowhere near the Andes, where the guinea pig originates.