Peanut (Arachis hypogaea)
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The peanut, or Groundnut (Arachis hypogaea) is a species in the legume family Fabaceae native to South America, Mexico and Central America.  It is an annual herbaceous plant growing to 30 to 50 cm (1 to 1½ ft) tall. The leaves are opposite, pinnate with four leaflets (two opposite pairs; no terminal leaflet), each leaflet 1 to 7 cm (⅜ to 2¾ in) long and 1 to 3 cm (⅜ to 1 inch) broad. The flowers are a typical peaflower in shape, 2 to 4 cm (¾ to 1½ in) across, yellow with reddish veining. After pollination, the fruit develops into a legume 3 to 7 cm (1 to 2 in) long containing 1 to 4 seeds, which forces its way underground to mature.
Although a nut in the culinary sense, in the botanical sense the fruit of the peanut is a woody, indehiscent legume and not a nut.
Peanuts are also known as earthnuts, goobers, goober peas, pindas, jack nuts, pinders, manila nuts and monkey balls. (The last of these is often used to mean the entire pod, not just the seeds. In the UK these are sold as monkey nuts.)
Evidence demonstrates that peanuts were domesticated in prehistoric times in Peru where wild ancestors are still found. Archeologists have thus far dated the oldest specimens to about 7,600 years before the present. Cultivation spread as far as Mesoamerica where the Spanish conquistadors found the tlalcacahuatl (Nahuatl=“earth cacao”=peanut, whence Mexican Spanish, cacahuate and French, cacahuète) being offered for sale in the marketplace of Tenochtitlan (Mexico City). The plant was later spread worldwide by European traders. Cultivation in the English colonies of North America was popularized by African Americans, who brought the Kikongo word “goober”. In South America, the peanut (called there maní or amendoim in Brazil) is thought to have first grown in Argentina or Bolivia, where the wildest strains grow today. In fact, many pre-Columbian cultures such as the Moche, depicted peanuts in their art. .
The peanut gained Western popularity when it came to the United States from Africa. It had become popular in Africa after being brought there from Brazil by the Portuguese around 1800.