early 14c., drounen, "suffocate by immersion in water or other fluid," also intransitive, "be suffocated by immersion (etc.)," also figurative, "to overwhelm or overpower by rising above as a flood," perhaps from an unrecorded variant of Old English druncnian (Middle English druncnen) "be swallowed up by water" (originally of ships as well as living things); at any rate it is probably from the base of drincan "to drink" (see drink (v.) and compare drench).
Or perhaps it is from Old Norse drukna "be drowned," which has at least influenced the modern form of the word, via North of England dialect. Related: Drowned; drowning. To drown (someone or something) out formerly was "to force to come out by influx of water;" in reference to sounds, by 1884.