The meaning of the title is a subject of much debate, as the term has historically been used as a nickname for several different things:
The track's energy has made it a favorite for movies and sports events, and it has been famously covered by other artists, including a speed-up version by the Australian band in 2004 that topped the charts in Australia. Ram Jam - Black Betty
It also referred to the "paddy wagon" or transport vehicle that carried inmates to prison. The meaning of the title is a subject
In Southern prisons, "Black Betty" was a common name for the bullwhip used by guards. Ram Jam - Black Betty