A garboon is a more specific racist term than
words such as "nigger" or "
coon". It refers to large black men (or women?) with particularly stereotypically "black" features, the likes of which would be found in a racist portrayal, e.g. enormous lips, wide and flat nose, extreme prognathism. Possible etymologies include the word "baboon" and "Gabon" (an African country) and the fact that the word sounds
like some species of ape.