“Jabberwocky” is a nonsense poem written by Lewis Carroll about the killing of a creature named “the Jabberwock”. It was included in his 1871 novel Through the Looking-Glass, the sequel to Alice’s Adventures in Wonderland (1865). The book tells of Alice’s adventures within the back-to-front world of the Looking-Glass world.
It’s not really nonsense. There are made up words but the gist of the story is a young man presumably a knight or prince goes out to slay a legendary creature and returns triumphant.