inhame

Yam comes from Portuguese inhame (a type of large tropical tuber), which was borrowed from a West African language — probably Wolof nyami or a related Senegambian language term meaning 'to eat' or 'food,' though there is also a proposed Fula connection through nyami. Some scholars derive it from Portuguese dialectal forms of 'tuber' or connect it to Spanish ñame (yam), which may have an independent African-language source. What is certain is that the word was transmitted through Portuguese — the Portuguese carried both the plant and the name for it from West Africa through their Atlantic trading networks. English may have received yam directly from Portuguese inhame or through one of the English colonial Caribbean settings where the plant had been introduced by the Portuguese and later the British slave trade. The first English attestation of 'yam' appears in the late sixteenth century in travel accounts of West Africa.

The true yam (genus Dioscorea) is a climbing plant native to the tropics of Africa, Asia, and the Americas, whose large starchy underground tubers are a dietary staple across the tropical belt. African yams — principally the white Guinea yam (Dioscorea rotundata) and the yellow Guinea yam (Dioscorea cayenensis) — were domesticated in West Africa possibly as early as 7,000 years ago and became the dietary foundation of the forest and savanna zones of West and Central Africa. A single yam tuber can weigh up to sixty kilograms, and the cultivation of yams in West Africa was embedded in deep cultural significance: yam festivals, yam-based social rituals, and the identification of the yam with masculine productivity and community prosperity were central to many West African cultures, particularly the Igbo of what is now Nigeria and the Akan of Ghana and Côte d'Ivoire.

Portuguese traders first systematically encountered West African yams along the Guinea coast in the mid-fifteenth century, and the plant's extraordinary productivity as a food source immediately attracted attention. Yams became one of the most important provisions for Portuguese slave ships crossing the Atlantic — the transatlantic slave trade's Middle Passage relied on yams as a primary food source for enslaved Africans, because the yam was familiar, calorie-dense, stored well, and could survive the weeks-long voyage without refrigeration. The yam therefore crossed the Atlantic not voluntarily but as the food of the enslaved, and it established itself in the Americas — particularly in the Caribbean, Brazil, and the American South — through the same networks of forced migration that brought the people who grew it. The word yam crossed the Atlantic with the plant and the people.

In the United States, the word yam acquired a complication from its encounter with the sweet potato (Ipomoea batatas), which is botanically a completely different plant — a member of the morning glory family, not the Dioscorea family. Enslaved African Americans in the American South began calling the orange-fleshed variety of sweet potato 'yam,' probably because its moist, sweet flesh resembled the yams they knew from West Africa more closely than the drier white-fleshed sweet potato. The USDA, responding to the commercial need to distinguish the two varieties of sweet potato in the market, formally designated the orange-fleshed sweet potato as 'yam' for marketing purposes, and this American usage has persisted to the day, creating the situation in which Americans routinely call sweet potatoes yams while the actual botanical yam (Dioscorea) — common throughout the Caribbean, Africa, and Asia — is almost unknown in mainstream American cooking.