Croaker

Noun

 * 1) One who croaks
 * 2) A vocal pessimist, grumbler, doomsayer.
 * 3) * 1915, Arthur Conan Doyle, The Valley of Fear
 * "It is my advice," the speaker continued, "that we go easier upon the small men. On the day that they have all been driven out the power of this society will have been broken." Unwelcome truths are not popular. There were angry cries as the speaker resumed his seat. McGinty rose with gloom upon his brow. "Brother Morris," said he, "you were always a croaker..."
 * 1) A frog
 * 2) A fish in the family Sciaenidae, known for the throbbing sounds they make.