In one of the Hardy Boys' mysteries, the brothers learn some jailbird slang. What is the slang word for "shut up", and what is the name of the book?

"arkitnay" is the slang word for shut up. The name of the book is "The Mystery of the Spiral Bridge"

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That's actually a combination of the British slang term 'nark it'- believed to come from Romany, as did many others - meaning 'shut up' and Pig Latin, which used (it is said) to be used by schoolboys so that the adults (who, of course, had never done the same thing when they were young) wouldn't understand them. I've never actually come across anyone who has used Pig Latin like this. It struck me as rather stupid when I first met it in a book.