Green’s Dictionary of Slang

(US) to perform second-rate, sloppy work; thus as n., a bodged job, a piece of do-it-yourself assembly.

1965		in DARE.
1993		J. Mowry Six Out Seven (1994) 29: Corbitt, Lamar, and Toby had built themselves one [i.e. a skateboard ramp] from scrap wood. It was a nigger-rig, and full of splinters, but it worked.
1994		(con. 1950s) in DARE File n.p.: The N-word showed up in a lot of places back home among the hillbillies (which is to say, us). To Nigger-rig was to improvise. . . as in ‘I had to nigger-rig that exhaust system, Cletus.’ [DARE].
2012		‘Dutch’ ? (Pronounced Que) [ebook] The way the bumper had been ‘nigguh-rigged’ with electrical tape and a chain to stay attached to the car.