past participle and former past tense of drink, used as an adjective from mid-14c. in sense "intoxicated, inebriated." In various expressions, such as drunk as a lord (1891), Drunk as a Wheelbarrow (1709); Chaucer has dronke ... as a Mous (c. 1386). Formerly also, of things, "drenched, saturated" (late 14c.). Meaning "a spree, a drinking bout" is by 1779.
Medieval folklore distinguished four successive stages of drunkenness, based on the animals they made men resemble: sheep, lion, ape, sow. Drunk driver first recorded 1948. Drunk-tank "jail cell for drunkards" attested by 1912, American English. The noun meaning "drunken person" is from 1852; earlier this would have been a drunkard.