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In the United States, the terms “yam” and “sweet potato” are used interchangeably, but they are completely different vegetables. Yams are starchy and have a rough, brown exterior. They can grow up to 45 feet long and are eaten in parts of Latin America, West Africa, the Caribbean, and Asia. Sweet potatoes are a New World root vegetable, have a softer, reddish skin, a creamier interior, and often, a darker interior. Most American supermarkets are selling you sweet potatoes, not yams. To find the yam that she was familiar with, Oduah had to trek to an African market that imported them from Ghana. 

The mix-up between yams and sweet potatoes originated from the Trans-Atlantic slave trade. Yams are an important part of West African food traditions. European slave traders steered their ships across the Middle Passage, they packed yams, along with black-eyed peas, to feed their captives. Slave merchant John Barbot estimated that 100,000 yams were required to sustain a ship bringing over 500 enslaved people, just 200 yams per person for a journey that could take months. In the Americas, where yams were not readily available, sweet potatoes, which had traveled from Central America with Christopher Columbus, took their place. As Dr. Scott Alves Barton, a chef and culinary educator who teaches at NYU, wrote in the February issue of Food & Wine , sweet potatoes became one of several transfer foods, a throughline allowing enslaved peoples to preserve their traditions and spiritual practices even in the face of captivity and abuse.

Even the word “yam” is an echo of the West African heritage of the vegetable—as Barton explained on a phone call, it has roots in the words “nyami,” “nyam,” or “enyame,” which mean, in different West African languages, literally, “to eat.” That’s how crucial yams were and are to the regional diet. “These foods in the African context have a religious significance, and a cultural heritage,” Barton said in a phone interview. “They gave the enslaved a reference.”