What does "sheepshead" mean?

Sheepshead: A large and valuable sparoid food fish (Archosargus, or Diplodus, probatocephalus) found on the Atlantic coast of the United States. It often weighs from ten to twelve pounds. Note: The name is also locally, in a loose way, applied to various other fishes, as the butterfish, the fresh-water drumfish, the parrot fish, the porgy, and the moonfish.