Origin and history of swan-song

"musical or rhythmic vocal utterance," Old English sang "voice, vocal music, song, art of singing; metrical composition adapted for singing, psalm, poem," from Proto-Germanic *songwho- (source also of Old Norse söngr, Norwegian song, Swedish sång, Old Saxon, Danish, Old Frisian, Old High German, German sang, Middle Dutch sanc, Dutch zang, Gothic saggws), from PIE *songwh-o- "singing, song," from *sengwh- "to sing, make an incantation" (see sing (v.)).

Of the musical call of some birds from late Old English. In literature often loosely, "poem focusing on arousal of emotions" of the sort traditionally sung to the lyre. Middle English had songly "worthy of song" (mid-14c.).

The colloquial phrase for a song "for a trifle, for little or nothing" is from "All's Well" III.ii.9 (the identical image, por du son, is in Old French). With a song in (one's) heart "feeling joy" is attested by 1859. Song and dance as a form of stage act is attested from 1872; the figurative sense of "rigmarole" is by 1895.

large, web-footed swimming bird, stately and graceful in the water, noted for its long neck and white down; 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 etymologically "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 the bird was sacred to Apollo and to Venus. The ancient Indo-European supernatural swan-maiden was so called by mythographers from 1829 (from German). Swan dive is recorded from 1898. Swanherd "one who tends swans" is late 15c. Swannage (late 14c.) was a payment for the right to keep swans.