The phrase manxome foe is taken from a nonsense poem called 'Jabberwocky'. The poem was written by Lewis Carroll (Charles Ludwidge Dodgson) and appears in his 1871 novel Through the Looking-Glass and What Alice Found There, a sequel to Alice's Adventures in Wonderland.
In the poem, which tells of the slaying of a monster called the Jabberwock, the phrase appears in the following lines:
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.
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The meaning of manxome may, of course, be decided by the individual reader. However, it has been suggested that it is a portmanteau word, made from manly and buxom.
Manxome Foe is also the title of a science fiction novel by John Ringo and Travis S. Taylor, which was published in 2008.