Hair of the dog
(n.) drinking to cure a hangover
The idea that a literal ‘hair of a dog’ has some kind of medicinal property probably comes from the misguided idea that bites from rabid animals could be treated by binding the wound with the creature’s hair or even blood, which dates back into antiquity. By the time the Tudor period rolled around, however, this ‘treatment’ had become nothing more than a figurative name for drinking to cure a hangover—that is, using the cause to cure its result.
The English writer John Heywood included the following in his collection of Proverbs in the English Tongue in 1546:
I praie the leat me and my felowe haue A heare of the dog that bote vs last nygh.
[I pray thee, let me and my fellow have a hair of the dog that bit us last night.]
That’s not to say that this was a purely English habit, of course. The lexicographer Randle Cotgrave included this entry under beste in his Dictionarie of the French and English Tongues in 1611:
Prendre du poil de la beste. To take a remedie for a mischiefe from that which was the cause thereof; as to go thin clothed when a cold is taken; or in drunkenness to fall a-quaffing, thereby to recover health, or sobrietie, neere unto which sense our Ale-knights often use this phrase, and say, Give us a haire of the dog that bit us.
Does it work? Well, various pseudoscientific theories claim that ethanol is better at breaking down the methanol and formaldehyde that are present in higher levels in the body after drinking than the body’s own enzymes—but why get technical when you’ve Samuel Pepys’ advice on your side:
…my head akeing all day from last night’s debauch. At noon dined with Sir W. Batten and Pen, who would have me drink two good draughts of sack to-day to cure me of last night’s disease, which I thought strange, but I think find it true.
Samuel Pepys’ Diary, 3 April 1661