This
database is a comprehensive collection of all the American idioms and slang available.
American Idioms are many and varied. We hope you enjoy our collection. We are adding more all the time.
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In Dante's Inferno, the ninth circle of hell is the centre where the worst punishments are found, so it is used idiomatically for something that couldn't get worse.
to refuse to incriminate oneself because of the protection of the Fifth Amendment of the Constitution of the United States (in the U.S. a witness at a trial has this right)
The business executive decided to take the Fifth rather than give testimony at the trial.