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curtains for, be.

Also, it's curtains. Be the end, especially death. For example, If he hadn't worn a bullet-proof vest, it would have been curtains for him, or It's curtains if she doesn't finish on time. This expression is a metaphor for the falling curtain signifying the end of a performance. [Slang; c. 1900]

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The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.