Everybody seems to have heard the word “mojo” but darned few white folks know what it means. Cecil Adams mumbled his way through theories that “mojo” means the sex act or a male sexual organ <…> after all, the first recording of “Got My Mojo Working” was made by Ann Cole, a woman! And the famous blues singer Robert Johnson had written about a woman’s mojo in “Little Queen of Spades,” way back in the 1930s. The truth is, the word has nothing to do with the sex organs of either gender and never has. So what is a mojo? It is, in short, the staple amulet of African-American hoodoo practice, a flannel bag containing one or more magical items. The word is thought by some to be a corruption of the English word “magic” but it more likely is related to the West African word “mojuba,” meaning a prayer of praise and homage. It is a “prayer in a bag” a spell you can carry.
Source: Hodoo in Theory and Practice by Catherine Yronwode