Idioms and Phrases with knock dead
Greatly amuse, astonish, or thrill someone, as in This new song will knock them dead. This slangy hyperbolic expression was first recorded in 1889. Also see knock the socks off.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.