Old English swan "swan," from Proto-Germanic *swanaz "singer" (source also of Old Saxon swan, Old Norse svanr, Danish svane, Swedish svan, Middle Dutch swane, Dutch zwaan, Old High German swan, German Schwan), probably literally "the singing bird" (from PIE root *swen- "to make sound"). If so, it is related to Old English geswin "melody, song" and swinsian "to make melody."
In classical mythology, sacred to Apollo and to Venus. The singing of swans before death was alluded to by Chaucer (late 14c.), but swan-song (1831) is a translation of German Schwanengesang. The ancient Indo-European mythical swan-maiden so called by mythographers from 1829. Swan dive is recorded from 1898.