Because enslaved Africans trafficked to the US would call sweet potatoes 'yams' as they looked so similar to the root vegetable that they ate at home in Africa but did not have in the US. Real yams are very starchy, with white flesh and a dark brown, bark-like skin.u003cbr/u003eu003cbr/u003eSo while fresh yams and sweet potatoes are different root vegetables, their names have been used interchangeably to describe this classic southern dish.