That's apocryphal actually, according to wikipedia:

The origin of "guinea" in "guinea pig" is unclear. One proposed explanation is that the animals were brought to Europe by way of Guinea, leading people to think they had originated there.[1] "Guinea" was also frequently used in English to refer generally to any far-off, unknown country, so the name may be a colorful reference to the animal's exotic origins.[27][28]

Another hypothesis suggests the "guinea" in the name is a corruption of "Guiana", an area in South America.[27][29] A common misconception is that they were so named because they were sold for the price of a guinea coin. This hypothesis is untenable because the guinea was first struck in England in 1663, and William Harvey used the term "Ginny-pig" as early as 1653.[30] Others believe "guinea" may be an alteration of the word coney (rabbit); guinea pigs were referred to as "pig coneys" in Edward Topsell's 1607 treatise on quadrupeds.[1]

They also just have lots of strange names in different languages