what is a swansong?

Answer 1

Here's a poem:

The wild swan's death-hymn took the soul
Of that waste place with joy
Hidden in sorrow: at first to the ear
The warble was low, and full and clear; ...
But anon her awful jubilant voice,
With a music strange and manifold,
Flow’d forth on a carol free and bold;
As when a mighty people rejoice
With shawms, and with cymbals, and harps of gold
And the tumult of their acclaim is roll’d
Thro’ the open gates of the city afar,
To the shepherd who watcheth the evening star...

Alfred, Lord Tennyson 1809–1892.

The Swan Song is supposed to be the hymn of the dying swan, but actually the swan finds out that it is going to a higher place of happiness and life and sings the most jubilant carol. It's like thinking that you're being handed your last hurrah and finding out midway that you've been selected for a much bigger production.
(That's always true if you keep having Faith, believing in yourself and the gifts that you have been given. In another song I always sing: walk on walk on with hope in your heart, or to reach, the unreachable star!)

Answer 2

Swan song is a reference to an ancient belief that the mute swan is completely mute during its lifespan, but may sing one song just before it dies.

Swan song is any final work or accomplishment.

Answer 3

It is a term given to someones last moment, like a last performance or before someones decline.

Answer 4

A farewell performance