Short answers, pulled from the story.
The Shorter Oxford English Dictionary gives a date of 1541 for the first recorded use of the word with the meaning to utter an oath sharply. This definition forms one of the foundations from which the musical style derives.
Isaac Hayes used the term on his album To Be Continued in 1970. His track Monologue Ike's Rap I featured husky-voiced spoken raps as key components of his sound.
DJ Kool Herc is identified as one of the first rappers at the end of the 1970s and he was a Jamaican immigrant who started delivering simple raps. He denied links to Jamaican toasting and claimed James Brown and Hustler's Convention were his inspiration instead.
Eminem created Lose Yourself in 2002 getting the first Oscar in Hip-Hop history. His flow remains dominant as of 2003.
Migos popularized this flow in 2014 though it is contentious within the community. The American hip-hop group Crime Mob exhibited a new rap flow in Knuck If You Buck heavily dependent on triplets before them.