Hey! This expression is also fairly common in English and means “someone or something that is used as the subject of an experiment.” However, how the expression came about is not quite certain.

A guinea pig is a small rodent that looks like a hamster that comes from the Andean region of South America. Therefore, the fact that it is called a “guinea pig” is quite odd since it is not a pig and it does not come from Guinea.

The “pig” part of the name may come from the claim that it bears some resemblance with a pig. Its Latin name also means “small pig.”

The “guinea” part of the name may be an allusion to Guineamen which were ships used in the slave trade. Another possibility is that Guinea was used to refer to any place far away across the sea.

Guinea Pig

At any rate, even though we do not know the reason why the guinea pig is named what it is, how did it come to describe someone or something that becomes the subject of an experiment? The answer is that many scientists used guinea pigs as subjects for their tests during the 19th and early 20th centuries.

The reason why they used guinea pigs instead of smaller animals like rats is not entirely clear. Eventually, the expression evolved so that it now refers to anything or anyone who is the subject of an experiment. It does not necessarily need to be an animal and it does not necessarily refer to a medical experiment.

This article talks about how soldiers have become the subjects of a military experiment that tests the effectiveness of anthrax in the event of a nuclear attack. 

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