yam (n.) Look up yam at Dictionary.com
1580s, igname (current form by 1690s), from Portuguese inhame or Spanish igname, from a West African language (compare Fulani nyami "to eat;" Twi anyinam "species of yam"); the word in American and Jamaican English probably is directly from West African sources. The Malay name is ubi, whence German öbiswurzel.