The term "deep-fried" was first used to describe foods in the United States in the 1930s. The practice was popularized in the 19th century, mainly in the south, where African-Americans often prepared chicken by boiling it in hot oil.
The practice of frying foods in oil is ancient, based on evidence from the fifth century BCE that suggests Egyptians deep-fried small cakes. A late medieval cookbook containing a recipe from Portugal demonstrates that Europeans were deep-frying fish before 1300, a practice that the Japanese adopted in the 17th century, when they invented tempura. In the 1830s, the Belgians and French deep-fried potatoes, and the English then paired deep-fried fish with "French" fries to give us "fish & chips." Deep-fried food really took off in the United States in 1930, when Harland Sanders of Kentucky started a chain of restaurants featuring deep-fried chicken. The deep-fried corndog made its first appearance in the 1940s.
One of the advantages of deep-fried foods is that, like most fast foods, they are portable. This make them a popular choice at outdoor festivals, including state fairs. By the1990s, innovators at state fairs across the country were experimenting with deep-frying nearly anything edible, including Twinkies, Snickers Bars, pickles and even globs of butter. In 2006 at the Texas State Fair, one vendor deep-fried Coca-Cola. More recent entries on the list of deep-fried foods available include Kool-Aid and bubble gum.