The peanut (Arachis hypogaea), also known as the groundnut, goober (US), goober pea, pindar (US), or monkey nut (UK), is a legume crop grown mainly for its edible seeds. It is widely grown in the tropics and subtropics by small and large commercial producers, both as a grain legume and as an oil crop. Atypically among legumes, peanut pods develop underground; this led botanist Carl Linnaeus to name peanuts hypogaea, which means "under the earth". Despite not meeting the botanical definition of a nut as "a fruit whose ovary wall becomes hard at maturity," peanuts are usually categorized as nuts for culinary purposes and in common English.

Source: Wikipedia