Candied yams aren’t really made with yams. In fact, all of our familiar American yam dishes are made with sweet potatoes. The darker orange, sweeter, moist varieties of sweet potato tend to be called yams in the U.S. while the more pale (white or yellow), firm & mealy, less-sweet ones are referred to as sweet potatoes. Most Americans have never even seen a true yam.
What’s a yam if not a type of sweet potato?
True yams come from Africa and go by the botanical name: Dioscorea. The name yam derives from the word nyami, also meaning to eat. Yams are starchy tubers; but only distant relatives of potatoes and unrelated to sweet potatoes—members of the morning glory family. The skin of a true yam is rough like bark, and can be poisonous if eaten raw.
So why do Americans call orange sweet potatoes yams?
In colonial Virgina (including North Carolina, the state that leads the US in sweet potato production), farmers took to calling the paler varieties of Ipomoea batatas sweet potatoes. African slaves in the colony used the word nyami to describe orange sweet potatoes, which bear some resemblance (but no relation) to true yams. Use of the abbreviated African word yam became widespread to differentiate sweet potatoes by color. The name yam has stuck for over 300 years, commonly used to describe the tastiest and most nutritious varieties of sweet potato to thrive on this continent.