In the wake of the President's use of "the N-word" in an interview with Marc Maron, I'd like to take this opportunity to encourage you to read Randall Kennedy's excellent 2008 book "Nigger: The Strange Career of a Troublesome Word." Its appearance in colloquial English was not only much earlier than I previously knew (I believe he traces it back to 1580-something) but originally it wasn't used in a derogatory way. Instead it was just a colloquialism or casual pronunciation of "negro", which is borrowed directly from the Spanish and Portuguese word for black. In most languages with some sort of familial ties to Latin words with "neg-" exist to refer to darkness or the color black. In any case, its journey from a stigma-free reference to skin color to the Word We Dare Not Name is an eventful and interesting one that Kennedy does a thorough job of taking the reader through.