Green’s Dictionary of Slang

(US) a black woman.

1848		Ladies’ Repository (N.Y.) Oct. VIII:37 316/1: Covess dinge, a negress.
1960, 1975		(ref. to 1850) Wentworth & Flexner DAS 123/2: covess dinge A colored woman.
1983		(ref. to 1850s) I.L. Allen Lang. of Ethnic Conflict 50: Status Diminution: covess-dinge [fem. 1850s. Covess, a woman, from cove, old slang for a fellow].