knock the bottom out of

knock the bottom out of (someone or something)

1. To undermine, weaken, or destroy something. The stock market crash knocked the bottom out of dozens of investment firms around the country. Tom's comments really knocked the bottom out of our proposal during the meeting.
2. To erode or undermine someone's self-confidence or sense of self-worth. Losing her job really knocked the bottom out of Sarah. I hope she comes out of this funk soon. Don't let boss's comments knock the bottom out of you. He's hard on everyone.
See also: bottom, knock, of, out
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

knock the bottom out of

Also, knock the props out from under. Render invalid, undermine. For example, The discovery of another planet that might support life knocks the bottom out of many theories , or Jane's skilled debating knocked the props out from under her opponent. The first expression dates from the late 1800s, the variant from the first half of the 1900s.
See also: bottom, knock, of, out
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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