(A) means a racoon, a small American animal valued for its fur. It is about the size of a fox, and lodges in hollow trees.
A gone coon. A person in a terrible fix; one on the verge of ruin. The coon being hunted for its fur is a “gone coon” when it has no escape from its pursuers. It is said that Colonel Crockett was one day out racoon-shooting in North America, when he levelled his gun at a tree where an “old coon” was concealed. Knowing the colonel's prowess, it cried out, in the voice of a man, “Hallo, there! air you Colonel Crockett? for if you air, I'll jist come down, or I know I am a gone 'coon.”
Martin Scott, lieutenant-general of the United States, is said to have had a prior claim to this saying.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894