The Monkey Gland Cocktail was detailed in "The Savoy Cocktail Book" (1930) compiled by Harry Craddock, an American bartender who plied his trade at London's Savoy Hotel while the United States was enduring Prohibition. The original recipe calls for absinthe, an anise-flavored spirit illegal here since 1912. These days sweeter substitutes for absinthe, notably Absente, Herbsaint or Pernod, are used in recipes calling for this spirit. The cocktail's name stems from a late-19th century practice of transplanting ape testicles into elderly men to renew their sex drive. Russian surgeon Serge Voronoff eventually performed more than 1,000 such procedures at $5,000 each.

When the Monkey Gland was introduced to America in a 1934 book, "The Official Mixer's Manual," by New York bartender Patrick Gavin Duffy, Duffy inexplicably chose Benedictine, a honeyed herbal liqueur said to have been developed in 1510 by the Benedictine monk Dom Bernardo Vincelli, to use as an accent in the drink instead of absinthe. This resulted in two versions of the cocktail, both with merit but very different from each other, becoming recognized as being authentic. Thus, the English Monkey Gland takes an absinthe substitute, and the American version calls for Benedictine.