There is NOTHING racial here. Guinea is a part of Eest Africa indeed. The reference is to the area, not to its population. Some gold likely came from there; the only common meaning of "guinea" in England was a gold coin worth 1 pound 1 shilling (modern 1.05 pounds), perhaps originally made in Guinea or from gold from Guinea, and it became a posh word for the sum of 1.05 pounds. - The guinea pig alias cavy didn't come from Guinea but from Peru and Bolivia. - The intended meaning of "guinea" in "guinea Cadillac" is clearly "cheap, simple", referring to the British guinea amount of money.