grog / gräg/ • n. spirits (originally rum) mixed with water. ∎ inf., alcoholic drink, esp. beer. ∎  crushed unglazed pottery or brick used as an additive in plaster or clay.

grog spirits (orig. rum) and water as served out to the Royal Navy. XVIII. Said to be from ‘Old Grog’', reputed nickname of the Admiral Vernon who gave the order in 1740 for the mixture to be used instead of neat spirit, derived from his wearing a grogram cloak.
Hence groggy intoxicated XVIII; (of a horse) diseased or weak in the forelegs; shaky, tottering XIX.

grog spirits (originally rum) mixed with water. The word, which is mid 18th century, is 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.

grog British naval drink; sugared rum mixed with hot water. Named after Admiral Vernon (early 18th century) whose nickname ‘Old Grog’ came from his grosgrain (heavy corded silk) coat.