The story
Of uncertain origin. Based on the common misconception that the order in which different kinds of alcoholic beverages are consumed necessarily causes hangovers or other ill effects.
Etymology from Wiktionary, CC BY-SA 4.0.
beer before liquor, never been sicker; liquor before beer, you're in the clear
Today it means: Drinking hard alcoholic beverages, such as liquor, before light alcoholic beverages, such as beer and wine, will not lead to a hangover, while the reverse order will. Full definition →