Swahili which I speak is not a Bantu language but has bantu words as well as Arabic and Portuguese. This mix is a direct result of these populations mingling on the coastal areas of East Africa. I have been to the old Portuguese forts on the coast. Those waters were also common passage for slaves going to Arabia.Language is usually an indication of origin, which can imply admixture. Haiti is more an exception to the rule. For the record, Swahili does not imply admixture. Swahili is a Bantu language that originates in Central/Southeast Africa:
"Swahili, also known as Kiswahili, is a Bantu language and the first language of the Swahili people. It is a lingua franca of theAfrican Great Lakes region and other parts of Southeast Africa, including Tanzania, Kenya, Uganda, Rwanda, Burundi, Mozambiqueand the Democratic Republic of the Congo.[7]"
The Swahili people are the direct lineage of these traders and locals who mixed. The language still spoken widely in east and central africa trully belongs to no one. I doubt you could get a Swahili person to call themselves a bantu they want their own autonomous state. A lot of central African countries adopted the language from the east because it is a unifier and belongs to all yet none. We all still have our ethnic dialects