What Does “knock them dead” mean?
Definition:
If you knock someone dead, you strongly impress them.
Origin
In its literal meaning, the phrase knock someone dead means to kill with a blow. But the phrase is mostly used figuratively, meaning to impress someone and affect them positively.
The phrase is often used in the theater. When comedians are about to perform, they are encouraged with the phrase knock them dead or with the abbreviated form of the phrase knock ‘em dead.
The relationship between the audience and comedians often reflects violent metaphors. In addition to the above phrase, performers often use terms like “killing” or “slaying” an audience when they perform well.
Knock the socks off is a variation of the phrase.
Example(s)
I would love to see you get up there and just knock ’em dead.
Their new album will knock them dead.
Knock ’em dead son, you’re the best!
