c.1600, Cornish name for a type of fish (also known as horse mackerel) abundant on the British coast; of uncertain origin, perhaps a variant of shad. OED compares Welsh ysgaden "herrings," Norwegian dialectal skad, Swedish skädde "flounder."
any of several species of fishes in the family Carangidae (order Perciformes), which also includes the jacks, amberjacks, and pompanos. The name scad is usually restricted to certain species in the genera Decapterus, Selar, and Trachurus. The half dozen species are marine and occur along the Atlantic coast of the Americas, except for the Mexican scad (D. scombrinus), which is found in the Pacific Ocean.