Given that some significant fraction of Africans traveling to the US back in the day were muzzies, the whole black muzzie thing in the US is more or less the real deal.
If you're referring to blacks traveling to the US back in the day as in his pop, sure, he was a Muslim.
If you're referring to the Nation of Islam, I don't think most Muslims are thrilled with them, not believing Fard Muhammad was the Mahdi. As to the origin, is it an offshoot of the Muslim faith brought over by slaves, interesting question, I don't know, but there's some logic to it.