A dictionary of Confusable Phrases: More Than 10,000 Idioms and Collocations

knock oneself dead • knock someone dead
knock oneself dead —(coll.) work very hard; make an extra
effort to accomplish smth. (also: knock oneself out): In the first
six weeks on the job I hardly spent one day in Pennsylvania.
…I had been all over the country, knocking myself dead.
knock someone dead —(coll., also: knock someone out) put on
a stunning performance; have a powerful emotional effect on
a person: This band is going to do great tonight. We’re going
to knock them dead.
knock someone off • knock someone out
knock someone off —
1
. make a person fall with a push: You’re
not safe on that ladder; a branch could knock you off. 2.
(Sport) defeat a competitor: If he can knock off the next two
opponents, he could get into the last part of the competition.
3. (sl.) kill a person: I don’t want to knock the old man off;
can’t we just tie him up to keep him quiet?
Note: 
The expression does not fully correlate in meaning with
the phrase knock someone off his feet—
1
. = knock someone off
1
: The sudden explosion of light, power, and thunder knocked
me off my feet and I landed hard on my back. 2. (coll.) have
a powerful emotional effect on a person: In addition to the per-
fect weather, the smell of the trees and good country air nearly
knocked me off my feet.
knock someone out—
1
. make a person unconscious by hitting
him: Scott’s reputation is excellent, and the managers fear that
he has been knocked out and robbed. 2. = knock someone off
2: Our team got through to the second part of the competition
before they were knocked out. 3. (coll.) tire a person very much
(through overwork): Hours of gardening in the sun have quite
knocked me out. Cf.: knock oneself out—(coll.) work very hard;
make an extra effort to accomplish smth.: We thank the one per-
son who knocked himself out making sure we enjoyed our-
selves. 4. (coll., also: knock someone dead) put on a stunning
performance; have a powerful emotional effect on a person: I
hadn’t heard of her show beforehand, but watched it imme-
diately and she knocked me out.