Green’s Dictionary of Slang

(US black) a fat, unattractive ‘black Mammy’ stereotype, supposedly typical of the West Indies.

1980		E. Folb Runnin’ Down Some Lines 145: Other terms for obese women, Bahama momma and Judy with the big bootie [...] suggest excessive girth and unattractiveness.
1992		R.C. Cruz Straight Outta Compton 26: Your big, fat Bahamma momma ain’t doin’ nuttin’ but sitting on her black behind.