guinea · noun1
From Guinea, the early modern name for West Africa, the coins originally being made of gold from the region, mostly from the 'Gold Coast' (modern Ghana) and used for African trade, and the guinea fowl being found there. Its use as an ethnic slur against Italians may be due to their darker complexion compared to people of Anglo-American descent.
Guinea · proper noun2
From Portuguese Guiné + -ia, the first part of which is of uncertain origin.
Etymology from Wiktionary, CC BY-SA 4.0.