yam

noun

1. the starchy, tuberous root of any of various climbing vines of the genus Dioscorea, cultivated for food in warm regions.
2. any of these plants.
3. the sweet potato.
4. Scot. potato(def 1).

noun

1. any of various twining plants of the genus Dioscorea, of tropical and subtropical regions, cultivated for their edible tubers: family Dioscoreaceae
2. the starchy tuber of any of these plants, which is eaten as a vegetable
3. Southern US any of certain large varieties of sweet potato
4. a former Scot name for the (common) potato

n.1580s, from Portuguese inhame or Spanish igname, from a West African language (cf. Fulani nyami “to eat;” Twi anyinam “species of yam”); the word in American and Jamaican English probably is directly from West African sources.