I think those ‘made-up’ names started off being a form of rebellion against the establishment (i.e. white society) during the 1960s. Notice that most people with names like the ones you mentioned are usually young; you will rarely see someone named ‘Keisha’ who is older than 35. In the beginning, authentic African/Islamic names were chosen, such as ‘Aisha,’ ‘Ayanna’ and ‘Jamal.’ Eventually, unique naming drifted from African roots as the lesser-educated and less politically-aware started doing it, and many names names were ‘invented’ or altered (i.e. ‘Anfernee = Anthony’) to maintain a distinction from the mainstream. Again, notice that black people with very elaborate names are usually from low-income backgrounds.