Funny, in Africa they have never celebrated "Kwanzaa" - and they would look at you funny if you asked them about it...
The best thing: Kwanzaa uses Swahili and Swahili is a language spoken in East Africa. The slaves came from West Africa.
A Nigerian fellow I worked with once asked: " Tell me. What is this Kwanzaa? We have never heard of it in Africa." I told him the truth, that some ex convict made it up.