May be wrong but my understanding is that 'rapping' refers to hip-hop's style of MCing, delivered with the appropriate enthusiasm of course. Referring to hip-hop as rap is so 80's lol...
The Jamaicans went a way to inventing 'MCing' in general by 'toasting' over dancehall reggae, but I've read articles that claim early rapping to be sourced in street acapella styles. I'm a big fan of the
Last Poets, who were early 70's. It has the social commentary of rap but it lacks the dance-oriented/crowd-moving MC element?