Fionnuala, daughter of Lir, was transformed into a swan, and condemned to wander for many hundred years over the lakes and rivers of Ireland till the introduction of Christianity into that island. T. Moore has a poem entitled The Song of Fionnuala. (Irish Melodies, No. 11.)
`What is that, mother?' `The swan, my love. He is floating down to his native grove ... Death darkens his eyes and unplumes his wings, Yet the sweetest song is the last he sings. Live so, my son, that when death shall come, Swan-like and sweet, it may waft thee home.'
Dr. G. Doane.
Swan. Mr. Nicol says of the Cygnus musicus that its note resembles the tones of a violin, though somewhat higher. Each note occurs after a long interval. The music presages a thaw in Iceland, and hence one of its great charms.
“Ethiopem vocamus cygnum.”
“ `What! is it my rara avis, my black swan?' ” —
Swan, a public-house sign, like the peacock and pheasant, was an emblem of the parade of chivalry. Every knight chose one of these birds, which was associated in his oath with God, the Virgin, or his lady-love. Hence their use as public-house signs.
N.B. Royal swans are marked with five nicks- two lengthwise, and three across the bill.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894