Just a theory mind you...but I think alot of this casual attitude toward the word itself began with the late great Richard Pryor. His stand up comedy was full of that word and (unless I've got the wrong guy) even the title of one of his one man shows was: 'That (N) is Crazy!

He was absolutely hilarious, no doubt about it and an inspiration for many who came after him, including the equally hilarious Chris Rock.

But I think Pryor was one of the first if not THE first to throw that word around like it was nothing and on top of that use it to be funny. He may have contributed to making it 'acceptable' at least to his own people.

Apple