Whats with the title?

J.R.R. Tolkien writes in the Lord of the Rings trilogy  when Frodo is honored with a song to celebrate his success in destroying the Ring of Doom.

And all the host laughed and wept, and in the midst of their merriment and tears the clear voice of the minstrel rose like silver and gold, and all men were hushed. And he sang to them…until their hearts, wounded with sweet words, overflowed, and their joy was like swords, and they passed in thought out to regions where pain and delight flow together and tears are the very wine of blessedness. (The Return of the King, 933)