Could possibly have been coined because of blacks in the early 60's financing Cadillacs and being unable to drive such a big car, necessitating a wide, arching turn at intersections, causing racists to call it a "Nigger Turn".
Guy #2: That was a major Nigger Turn!
Guy #1: He covered every lane with that turn... biggest Nigger Turn I've ever seen!
Guy #3: That was an Asian guy, not a black guy!
Guy #1: Dude, it doesn't matter what color person is driving the car, if you turn and sweep every lane, that's a Nigger Turn!
"Don't Nigger Turn into my driveway it fucks up the curbs jackass"