"magic," 1920s, probably of Creole origin; compare Gullah moco "witchcraft," Fula moco'o "medicine man." It was noted in 1935 as an underworld name for "any of the poisonous, habit-forming narcotics."
type of rum-based Cuban cocktail, by 1946, from Cuban Spanish, a diminutive of mojo, a word for certain sauces and marinades; Ayto ("Diner's Dictionary") considers it to be "probably a reapplication of the Spanish adjective mojo 'wet,'" from mojar "to moisten, make wet," from Vulgar Latin *molliare"to soften by soaking," from Latin mollire "to soften" (see emollient).
I don't know who originated this one, but every bar in the West Indies serves it, practically every rum recipe booklet gives the formula for it, so my little collection of rum drinks would hardly be complete without it. Such popularity must be deserved, and it is. It's a swell drink! ["Trader Vic's Book of Food and Drink," 1946]