Green’s Dictionary of Slang

nigger-lover n.

[nigger n.1 (1) + SE lover]

[mid-19C+] (orig. US) a term of abuse, aimed at a white who is seen as overly friendly towards blacks.

In derivatives

nigger-loving (n.)

[late 19C+] (US) a derog. term for the refusal of whites to take a racist attitude to blacks.

nigger-loving (adj.) (US)

1. [late 19C+] used of any white person showing favour to black people.

2. [1960s+] used as a general derog. epithet, usu. by Southerners, irrespective of the object’s actual racial opinions.