This cocktail is a 'hair of the dog' hangover cure, which is why it has this name. It first appeared in the Savoy Cocktail Handbook by Harry Craddock in 1930.
2 parts Cognac
1 part Applejack
1 part Sweet Vermouth
Mix ingredients. Stir with ice. Strain into a chilled cocktail glass.
Serve straight up in a cocktail glass.
How to make the Corpse Reviver #1 cocktail
A Hair of the Dog:
I pray thee let me and my fellow have
A hair of the dog that bit us last night
And bitten were we both to the brain aright.
We saw each other drunk in the good ale glass.
~ John Heywood, 1546
The Savoy Cocktail Book