Hair of the dog

Refers to a little of the alcohol that one imbibed the day before the hangover, taken as a cure for the latter. Used in this figurative sense, it derives from John Heywood’s Proverbs published in 1546 where it appears in full as, “A hair of the dog that bit us.” The literal sense goes back to at least Roman times when people believed that a dog-bite could be cured, even if rabid, by placing a hair of the dog in question over the wound.