Grog
mid 18th century: said to be from Old Grog, the reputed nickname (because of his grogram cloak) of Admiral Vernon (1684–1757), who in 1740 first ordered diluted (instead of neat) rum to be served out to sailors.
wiktionary
An allusion to Admiral Edward Vernon (nicknamed “Old Grog” after the grogram coat he habitually wore), who in 1740 ordered his sailors' rum to be watered down. [1] [2]
This etymology is incomplete. You can help Wiktionary by elaborating on the origins of this term.
etymonline
grog (n.)
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.
