I've heard it used in some shows as a derogatory slang term towards Italians in shows like the Soprano's. What's the relationship between Italians and the word?
From the 1600s onwards, Guinea was used as a geographic term for the coast of west africa. That terminology survives in the modern republics of Guinea, Guinea-Bissau and Equatoreal Guinea.
According to the Online Etymology Dictionary, the use of the term as an insult against Italians is most likely an allusion to their darker complexion as compared to Anglo-Americans. The insult was to over-emphasize the darker complexion, and imply West African ancestry as the cause.
