knock oneself out


1

Make a great effort, as in I was knocking myself out to finish on time. This expression also is put negatively, Don't knock yourself out, meaning “don't exert yourself; it's not worth that much effort.” [c. 1930]

2

Enjoy yourself, have a good time, as in You're off to Europe? Knock yourself out. [Slang; mid-1900s] Both usages allude to knocking oneself unconscious (see knock out). For a synonym see break one's ass.

QUIZZES

WHO SAID IT: A QUIZ ON PRESIDENTIAL WIT AND WISDOM

Think you know your presidents? Take this quiz and see if you can match the style, wit, and ideology of these memorable lines to the right POTUS.
Question 1 of 9
“I do believe that the buck stops here, that I cannot rely upon public opinion polls to tell me what is right. I do believe that right makes might and that if I am wrong, 10 angels swearing I was right would make no difference.”
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.