Hair of the dog is a colloquial English expression predominantly used to refer to alcohol that is consumed with the aim of lessening the effects of a hangover. It is a shortened form of the expression “the hair of the dog that bit you.” The phrase “bite the dog that bit you” is also commonly used in this sense. The origin of the phrase is literal, and comes from an erroneous method of treatment of a rabid dog bite by placing hair from the dog in the bite wound.