What does "croaker" mean?

Croaker: (Zoöl.) (a) A small American fish (Micropogon undulatus), of the Atlantic coast. (a) An American fresh-water fish (Aplodinotus grunniens); -- called also drum. (c) The surf fish of California. Note: When caught these fishes make a croaking sound; whence the name, which is often corrupted into crocus.