What is the origin of the idiom "guinea pig" and when to use it?

The idiom "guinea pig" has its origins in the early 17th century when guinea pigs were first introduced to Europe. These small rodents are not native to Guinea but were imported to Europe via Guinea, a region in West Africa. The exact reason for the association with Guinea remains unclear, but it is believed that European traders may have used the term "Guinea" to refer to any distant or exotic place. Guinea pigs were considered exotic animals when they were first brought to Europe, and the name likely reflects their foreign origin. In modern English, "guinea pig" is used metaphorically to refer to a person or creature used in experiments, tests, or trials to gather information or conduct research, often at some risk to their well-being.