Definition of coon

1:  raccoon

2: offensive —used as an insulting and contemptuous term for a black person

I would say a more comprehensive current use is basically the same as an Uncle Tom, someone who lives to please white people, or someone who lives by very limiting black stereotypes, very unaware.

But where does it come from?

That gets a little hazy! So, here are some possible roots of the word.

Colombia.edu has a very interesting piece entitled “African American Songwriters and Performers in the Coon Song Era: Black Innovation and American Popular Music” and here is an excerpt:

James H. Dorman says in American Quarterly that coon songs featured blacks “as not only ignorant and indolent, but also devoid of honesty or personal honor, given to drunkenness and gambling, utterly without ambition, sensuous, libidinous, even lascivious.” Generally performed in dialect, coon songs employed “catchy’ rhythms,” and were meant to be “hilariously funny.” [3] Russell Sanjeck dates the first use of the term coon—”the now distasteful word in popular music”—as 1834, with the publication of banjo-playing minstrel performer George Washington Dixon’s song “Old Zip Coon.” [4] As a character, Zip Coon was a somewhat scary citified dandy—in stark contrast to his more innocent rural counterpart, Jim Crow. The word coon as a short form for raccoon dates from 1741, and before Dixon’s use of coon it meant a “frontier rustic.” [5] In 1767, a black character named “Raccoon” sang a version of “Yankee Doodle Dandy” in the first British opera published in America. [6] Several generations later in 1840, the Whig party (established to counter the strong presidency exerted by Andrew Jackson) used the raccoon as its political symbol. Coon songs in the 1840s and 50s were merely Whig political songs, but by 1862 the term “had come to mean a Black.” [7] One explanation for this is, according to the American Dictionary of English (1944), that it denoted “the name of the animal which Southern Negroes were supposed to enjoy hunting and eating.” [8] In The Wages of Whiteness, David R. Roediger argues that the term coon, like “buck” and “Mose,” became a racial slur only “gradually.” [9] The Parlor Songs Association also insists that the term was not a racial slur originally but rather “evolved into that” with some additional confusion: some contemporary composers who didn’t know better confused the raccoon with the possum, often using the two animals interchangeably. There is, however, no existing legacy for the “possum song.” [10]

Source: http://www.columbia.edu/cu/cjas/salem1.html

There there is the possibility that it originates from a Portuguese word that came into use in the United States. The word was barracoon, which meant a barrack, set of buildings or enclosures used to hold slaves or convicts.

In the infamous Uncle Tom’s cabin there is also a reference to the word that means escaped slaves “Well, Tom, yer coons are fairly treed.”