My wife and I are still reading Patrick O’Brian’s Aubrey-Maturin series (we’re most of the way through the fourth novel, The Mauritius Command), and naturally we hear a fair amount about grog. I’ve seen the etymology of the word before but had forgotten it, and since it’s surprising and Asya Pereltsvaig tells it well at Languages of the World, I’ll quote her post for the edification and delectation of all and sundry:
Take the word groggy: today it describes someone who’s shaky, dizzy or sluggish, as from a blow or from the lack of sleep, as well as someone experiencing similar symptoms due to being drunk (that’s the earlier meaning, as we shall see immediately below). But the history of this word goes back to a rather unexpected place: the French expression gros grain meaning ‘coarse grain’. It is from this expression that the name of the coarse fabric grogram derives. Still, how did we get from a coarse fabric to being dizzy and sluggish? The crucial figure in this tortuous path is Admiral Edward Vernon of the British Navy, known to sailors as “Old Grog”, for he often wore a coat made of grogram (note that the shortening of grogram to Grog follows the same path of clipping that leaves behind a non-morpheme, as in the case of blog from weblog).
It was Admiral Vernon who in 1740 ordered water to be added to the ration of rum served to the sailors under his command; to cut down on the water’s foulness, lemon or lime juice was also added, which led to lowering the incidence of scurvy, even though the connection was not yet understood at the time. The rest of the Royal Navy rapidly followed Vernon’s lead, and eventually the Admiral’s nickname grog became associated with the drink itself, rum diluted with water. A sailor drunk on grog was called groggy, and eventually the meaning of this word was extended from a more specific to a more general one to include a hazy and dizzy state from any cause.
(The remainder of Asya’s post has interesting stuff about cheese, foie gras, and other things and is well worth reading.)