Derived from the original abbreviation "MC," now used as the generic term for anyone who speaks over a beat, or performs songs that could be termed "hip-hop." Afrika Bambaataa and his contemporaries at the Universal Zulu Nation were the first to exemplify this term.
Originated as a term for the only individual at a party who could speak on the microphone while the DJ (Disk Jockey) was looping the hook or the beat. Various individuals claim that MC stands for the following:
1: Master of Ceremonies, generally the speaker presiding over a formal gathering, or the host of a Jamaican gameshow.
2: Move the Crowd. Originally proclaimed by the legendary emcee Rakim (of the group Eric B. and Rakim) on his 1986 urban hit "Eric B. Is President;" to Rakim, an MC was any rapper who was able to control the crowd that he was presiding over.
3: Microphone Controller.
4: Mic Checka
1b: "The term, MC, stand for Master of Ceremonies" - A Tribe Called Quest, Midnight Marauders
2: "To me, M.C. means Move the Crowd" - Rakim, Eric B. Is President
"I'm, the Nineteen Naughty Nine MC
Microphone controller, master of ceremonies" - Naughty by Nature, Holiday
An emcee is, in effect, the person(s) who speak and are the head of a show or performance.