1749, "alcoholic drink diluted with water," supposedly a reference to Old Grog, nickname of Edward Vernon (1684-1757), British admiral who wore a grogram (q.v.) cloak and who in August 1740 ordered his sailors' rum to be diluted. George Washington's older half-brother Lawrence served under Vernon in the Caribbean and renamed the family's Hunting Creek Plantation in Virginia for him in 1740, calling it Mount Vernon. Eventually the word came popularly to mean "strong drink" of any kind. Grog shop "tavern where alcohol is sold by the glass" is from 1790.
updated on April 21, 2015