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knock someone's block off

Beat up someone, as in If he doesn't leave at once, I'll knock his block off. This hyperbolic term employs block in the sense of “head,” a usage dating from the 1600s. The idiom, however, dates only from about 1900. Also see beat the living daylights out of.

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The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.