Mojo is originally Black English, first recorded in the mid-1920s. From Puckett’s 1926 Folk Beliefs of the Southern Negro:
The term mojo is often used by the Mississippi Negroes to mean “charms, amulets, or tricks,” as “to work mojo” on a person or “to carry a mojo.”
The word mojo is common throughout the American South and the Caribbean. The meaning has always been magic, a charm or amulet, or more broadly power and influence, often sexual power, derived from such a supernatural source.
The exact origin of mojo is unknown, but it seems likely that it is African in origin. Gullah (the dialect of the South Carolina Atlantic islands) has the word moco meaning witchcraft or magic. And the Fula language of Africa has the word moco’o meaning a shaman.
(Source: Oxford English Dictionary, 3rd Edition)
Copyright 1997-2016, by David Wilton