From Middle English swan, from Old English swan, from Proto-Germanic *swanaz. Cognate with West Frisian swan, Low German Swaan, swan, Dutch zwaan, German Schwan, Norwegian svane, Swedish svan, probably literally “the singing bird”, from a Proto-Indo-European *swon-/*swen- (“to sing, make sound”). Related to Old English geswin (“melody, song”) and swinsian (“to make melody”). Compare Latin sonus (“sound”) and Russian звон (zvon, “ringing”) and звук (zvuk, “sound”).
From Proto-Germanic *swanaz, probably from Proto-Indo-European *swen- (“to sound, resound”). Compare Old Saxon swan (Low German Swaan), Dutch zwaan, Old High German swan (German Schwan), Old Norse svanr (Swedish svan).
From Old Frisian *swan, from Proto-Germanic *swanaz, probably from Proto-Indo-European *swen- (“to sound, resound”).