Green’s Dictionary of Slang

Nigerian n.

(gay) a black man.

1972		B. Rodgers Queens’ Vernacular.
1983		I.L. Allen Lang. of Ethnic Conflict 48: Allusions to African Origins: nigerian [ostensibly from Nigerian but serves as a euphemism for nigger].

In compounds

Nigerian lager (n.) [its blackness]

Guinness stout.

1977		D. Powis Signs of Crime 194: Nigerian lager Guinness stout.
1989		J. Morton Lowspeak.