[Isamu]

I had to look it up:

“Be careful not to confuse tortuous with torturous. These two words are relatives—both ultimately come from the Latin verb torquere, which means "to twist," "to wind," or "to wrench"—but tortuous means "winding" or "crooked," whereas torturous means "painfully unpleasant."

[viherjuuri]

Cool! That is probably the joke that is being made in the book. And it is funny.