Grog is any of a variety of psychoactive beverages, mostly alcoholic beverages. The word originally referred to rum diluted with water, which British Vice-Admiral Edward Vernon introduced into the naval squadron he commanded in the West Indies on 21 August 1740. Vernon wore a coat of grogram cloth and was nicknamed Old Grogram or Old Grog.

Modern versions of the drink are often made with hot or boiling water, and sometimes include lemon juice, lime juice, cinnamon, or sugar to add flavor.

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