croaker

noun

1. Someone who or something that makes a croaking sound.
2. Any of certain fish in the family Sciaenidae, known for the throbbing sounds they make.
3. (informal)A frog.

   “Frogs are also sensitive to vibrations through the ground, a footfall usually being sufficient to instil silence in a pond full of croakers.”

4. (slang)A doctor.

   “"Lungs," said McGuire comprehensively. "I got it. The croaker says I'll come to time for four months longer—maybe six if I hold my gait.[…]"”

   “He located a doctor in Brooklyn who was a writing fool. This croaker would go three scripts a day for as high as thirty tablets a script.”

5. (slang)One who will soon die; a goner.

   “Mrs. Burke had […] bought a bottle […] to comfort him in his dying struggles (she was sure he must be a 'croaker').”

6. (dated)A vocal pessimist, grumbler, or doomsayer.

   “There are croakers in every country, always boding its ruin.”

   “It is thought by many, and said by some, that this Republic has already seen its best days; that the historian may now write the story of its decline and fall. Two classes of men are just now especially afflicted with such forebodings. The first are those who are croakers by nature – the men who have a taste for funerals, and especially national funerals. They never see the bright side of anything, and probably never will.”

   “Nor did the croakers have long to wait. The second night after the drowning of the mate the little yacht was suddenly wracked from stem to stern.”

   “"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..."”