To your point, they start with nursery rhymes.  Here is an example: Humpty Dumpty sat on a wall.  Humpty Dumpty had a Great Fall.  All the kings horses and all the kings men couldn't put Humpty together again. -  Humpty Dumpty = Dumb Humans Humpty also featured, coincidentally, in Lewis Carroll's "Through the Looking Glass'.   "When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to mean—neither more nor less."     "The question is," said Alice, "whether you can make words mean so many different things."     "The question is," said Humpty Dumpty, "which is to be master—that's all." And it is this principle that they use in their spells.  Words have different meanings.  Which meaning is master is what matters to them.