Jabberwocky is a poem in a book, sort of nested fiction. In chapter one of Lewis Carroll's Through the Looking Glass and What Alice Found There, Alice happens upon it inside a book.
"It seems very pretty," Alice said when she had finished it, "but it's rather hard to understand! ... Somehow it seems to fill my head with ideas--only I don't exactly know what they are!"
It may be nonsense, but Carroll's use of letter patterns and sounds that suggest things is neat. My Random Word Generator toy uses the same principles.