i found this answer on yahoo answers;
"Whatever the reason, this perception of pigginess occurred in many languages other than English; the German word for them is Meerschweinchen, literally "Little Sea Pigs" (sailing ships stopping to reprovision in the New World would pick up stores of guinea pigs, which provided an easily transportable source of fresh meat), the Russian and Polish word for them is similar, "morskaya svinka" and "winka morska" respectively, meaning also "Little Sea Pig" (it comes from archaic use of the word to mean "overseas"). The French word is Cochon d'Inde, (Indian pig), the Dutch used to call it guinees biggetje (Guinean piglet), and in Norway, Sweden and Denmark they are called marsvin (a combination of the Latin word mare for ocean, and Norwegian/Swedish/Danish svin which means pig). In Greek they are called 'indika xoiridia' (Small Indian Pigs), and in Portuguese, the term is "porquinho ** �ndia", literally "little pig of the Indies". In Italian the term is either "Porcellino D'India" (Little Indian Pig) or "Cavia Peruviana" (Peruvian Cavy). However, this perception of pigginess is not universal to all languages or cultures. For example, the common Spanish word is 'conejillo de Indias' (Indian bunny rabbit).
The scientific name of a common species is Cavia porcellus, with porcellus being Latin for "little pig".
The origin of "guinea" in "guinea pig" is even harder to explain. One theory is that the animals were brought to Europe by way of Guinea, leading people to think they had originated there. Another theory suggests that "Guinea" in the case of the guinea pig is a corruption of "Guiana", an area in South America. A common misconception is that they were so named because they were sold as the closest thing to a pig one could get for a guinea (an old British coin with a value of 21 shillings, or 1.05 GBP in modern decimal currency). However, evidence does not support this conjecture: for example, the Dutch name refers to the country of Guinea rather than the British coin, and the first guinea pig was described in 1554 by the Swiss naturalist Konrad Gesner more than a hundred years before the first guinea was struck."
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