Jabberwocky

Jabberwocky is a 'nonsense poem' written by Lewis Carroll in his 1871 novel "Through the Looking-Glass". All the same, it does strangely make a kind of sense.
In an early scene of Alice in Wonderland, Alice finds the verse "Jabberwocky". She says (p24)
"Somehow it seems to fill my head with ideasonly I don't exactly know what they are.”
This is now thought to be one of the greatest nonsense poems written in English. Its playful, whimsical language has given us nonsense words, portmanteau words and neologisms such as "galumphing" and "chortle".
Origin and publication.
The concept of nonsense verse was not original to Carroll. Nonsense existed in Shakespeare's work and was well known in the Brothers Grimm's fairytales, some of which are called lying tales or "lügenmärchen". 
John Tenniel reluctantly agreed to illustrate the book in 1871, and his illustrations are still the defining images of the poem.
The illustration of the Jabberwock may reflect the Victorian obsession with natural history and the fast-evolving sciences of palaeontology and geology. The works of Darwin and the models of dinosaurs at the Crystal Palace Exhibition helped feed the interest. Perhaps it is not so surprising that Tenniel gave the Jabberwock "the leathery wings of a pterodactyl and the long rough neck and tail of a sauropod".
The poem.
Jabberwocky
'Twas brillig, and the slithy toves
Did gyre and gimble in the wabe;
All mimsy were the borogoves,
And the mome raths outgrabe.
"Beware the Jabberwock, my son!
The jaws that bite, the claws that catch!
Beware the Jubjub bird, and shun
The frumious Bandersnatch!"
He took his vorpal sword in hand:
Long time the Manxome foe he sought—
So rested he by the Tumtum tree,
And stood awhile in thought.
And as in uffish thought he stood,
The Jabberwock, with eyes of flame,
Came whiffling through the tulgey wood,
And burbled as it came!
One, two! One, two! and through and through
The vorpal blade went snicker-snack!
He left it dead, and with its head
He went galumphing back.
"And hast thou slain the Jabberwock?
Come to my arms, my beamish boy!
O frabjous day! Callooh! Callay!"
He chortled in his joy.
'Twas brillig, and the slithy toves
Did gyre and gimble in the wabe;
All mimsy were the borogoves,
And the mome raths outgrabe.
Many of the words in the poem are playful words of Carroll's own invention, without special meaning. When Alice has finished reading the poem she gives her impressions: 
'It seems very pretty,' she said when she had finished it, 'but it's rather hard to understand!' (You see she didn't like to confess, even to herself, that she couldn't make it out at all.) 'Somehow it seems to fill my head with ideas—only I don't exactly know what they are! However, somebody killed something: that's clear, at any rate'
In "Through the Looking Glass", the character of Humpty Dumpty explains to her the nonsense words from the first stanza of the poem. However, Carroll's personal commentary on several of the words differ from Humpty's. An analysis of the poem and Carroll's commentary is given in the book "The Annotated Alice" by Martin Gardner.