In ancient Greek mythology, Apollo was the sun god and god of light. Because of its versatility, it is also the god of poetry and music, and later generations regard it as the patron saint of literature and art. Swan is the god bird of Apollo, so it is often used as a metaphor for literature and art. It is said that swan never sings, but it will hold its neck and sing a song before it dies. Its songs are sad and touching. This is the only and last time it sings in its life. Therefore, western countries use this allusion to describe a masterpiece of poets, writers and composers, or the last performance of actors and singers. That is to say, the last or farewell appears; The last work before death; Occasionally, it can also refer to the last remnant of something.
The swan song is an ancient idiom with a long history. As early as the 6th century BC, there was a saying in the fable of Aesop, an ancient Greek fable writer, that "swans sing only when they are dead". Cicero (BC 106- 43), an ancient Roman politician and writer, used the "swan song" as a metaphor for the elegy of death in his papers, such as On the Philosophy of De Kenlun Villa. In Britain, Chaucer, Shakespeare and other great poets and playwrights have used this idiom. For example, the image of Emily portrayed in Shakespeare's famous tragedy Othello dares to expose her husband's crimes in Death. When she died, she compared herself to a swan and sang only one song in her life.