Deviled describes a dish or ingredient that has been seasoned with a spicy or zesty condiment-based mixture, typically built on mustard, cayenne pepper, black pepper, or hot sauce. The term likely originated in 18th-century England, where highly seasoned, fiery dishes were called "deviled" for their association with the heat and bite of the devil; it caught on widely in 19th-century American cooking.
Deviling usually means coating or stuffing a protein - eggs, ham, crab meat, chicken, or shrimp - with a spicy, pungent mixture of mustard, Worcestershire sauce, paprika, or similar seasonings. Deviled eggs are the best-known example; deviled ham and deviled crab apply the same idea to spreads and baked fillings. Regional variations exist, such as adding Old Bay seasoning in the American South.