Actually, such speech is of British Isles origin and has been used by whites in the past. Recall the "stereotypical" feudin' hillbillies in that Bugs Bunny cartoon where the hillbilly says "Be ye a Hatfield, or be ye a Coy rabbit?" Pirates are also sterotyped as speaking that way.
Similarly "ax" is Chaucerian Middle English and is used by whites in New Orleans.
Black English doesn't come from Africa. It comes from England and preserves anachronistic features of classes of British English speakers of former times.
As described in detail in Thomas Sowell's book 'Black Rednecks and White Liberals'.