The words in The Tempest that appeal most to Holling are the curses that the character Caliban utters. Holling likes them because they're the most original, interesting-sounding cuss words he's ever come across. As Holling says, "I mean, he really knew cuss words."
Caliban's cuss words aren't the kind that you're probably used to hearing. They're full phrases, such as "The red plague rid you!" and "A southwest blow on ye and blister you all o'er!"
Holling decides to practice delivering these curses, choosing to first try out "Toads, beetles, bats, light on you!" because, as he says, it's the one he understands the best.
Holling practices Caliban's curses at home on his parents and sister. He practices some more at school. When he passes Mr. Guareschi in the hallway as he's trying to get the rats out of the ceiling, Holling nicely suggests that instead of the four-letter word Mr. Guareschi lets fly, he could try, "The red plague rid you!"
When Mrs. Baker asks Holling why he's so fond of the curses, he tells her he likes the rhythm of them. As readers, we get the impression that Holling is too good a boy to let loose with the kind of expletives that will normally get a kid sent to the principal's office. But perfecting his delivery of Caliban's curses lets him vent some of his anger and intense feelings in a way that won't get him in trouble, and also in a way that's more expressive than any four-letter word.
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