Hi , knopflerized and Lestroid. If you continue to look at the Wiki article, there was another possible definition which might also play in here.
"In 1934, John A. and Alan Lomax in their book, American Ballads and Folk Songs described the origins of "Black Betty":
"Black Betty is not another Frankie, nor yet a two-timing woman that a man can moan his blues about. She is the whip that was and is used in some Southern prisons. A convict on the Darrington State Farm in Texas, where, by the way, whipping has been practically discontinued, laughed at Black Betty and mimicked her conversation in the following song." (In the text, the music notation and lyrics follow.)[8]
John Lomax also interviewed blues musician James Baker (better known as "Iron Head") in 1934, almost one year after recording Iron Head performing the first known recording of the song.[9] In the resulting article for Musical Quarterly, titled "'Sinful Songs' of the Southern Negro", Lomax again mentions the nickname of the bullwhip is "Black Betty".[10] Steven Cornelius in his book, Music of the Civil War Era, states in a section concerning folk music following the war's end that "prisoners sang of 'Black Betty', the driver's whip."[11]"
What I have always thought was that that whip probably snapped very fast and viciously - bamalam when it landed. From all reports, Sonny's fist was also very fast and could do vicious damage when it landed!
Anyway, that is my take on the matter. And thanks, Lestroid, for the link to the interview. I also had not seen it previously.