'Swan' is PIE *swen- (to sound) — the bird named as 'the singer.' The swan song is in the etymology.
A large waterbird with a long flexible neck, short legs, and typically all-white plumage.
From Old English 'swan' (swan), from Proto-Germanic *swanaz (swan), probably from PIE *swon- or *swen- (to sing, to sound, to make a tone). The swan was 'the singer' or 'the sounder' — named for its call. This connects to the ancient belief in the 'swan song': that a swan sings beautifully just before death, a belief recorded by Plato, Aristotle, and Aeschylus, and reflected in the compound 'swan song' (a final, finest performance). Key roots: *swen- (Proto-Indo-European: "to sound, to sing, to make a tone").
The phrase 'swan song' (a final masterpiece before death) reflects the ancient Greek belief that mute swans, silent throughout their lives, sing one hauntingly beautiful melody as they die. Plato records Socrates mentioning it. The belief is not entirely false: mute swans do produce a distinctive musical sound with their wings in flight, and whooper swans have a genuinely melodic call. The etymology