Green’s Dictionary of Slang

(US) a black person; also as adj.

1969		in Current Sl. IV:3–4 (1970).
1971		E.E. Landy Underground Dict. (1972).
1983		I.L. Allen Lang. of Ethnic Conflict 49: Other Cultural Allusions: mayate [or mayata. From Chicano Spanish mayate, a U. S. black person].
1992		Bentley & Corbett Prison Sl. 55: Mayate A black person.
2006		F.X. Toole Pound for Pound 129: They hated the mayate black shitbug.
2019		D. Winslow Border [ebook] If you were a ‘baby,’ a bitch [...] carnals or camaradas weren’t allowed to use your services. That was for peckerwoods or mayates, not for proud, macho Mexican men of la raza.