Yes, I acknowledge the disconnection from their ancestry. However, descendants of black slaves in other countries (the US is not the only country with descendants of black slaves) have not followed the same route to new unique and identifying names.
Moreover, you don't have to pick something randomly, you can look at names, read about their meanings and pick something that sounds nice to you. you don't do it in a vacuum. So, my question is why this alternative, vs, any other alternative at creating self identification?
PS never mind that in some countries you can't just make up names. You can use foreign names, but you have to prove they are viable names in the place you claim them to be used names. But that's beside the point.
And, of course, keep in mind, all names were somewhat "invented" and new at some point in time. My question is more about how/why did this method (of prefixes, among other unique qualities) predominate over other available methods?
Also, curiously, many Africans with their ancestral surnames will have a European forename along with an African middle name.