1
general::
Phrase(s): curtains for someone or something
the death, end, or ruin of someone or something. (From the lowering or closing of the curtains at the end of a stage performance.) • If the car hadn’t swerved, it would have been curtains for the pedestrians. • If they can’t get into the export market, it’s curtains for the whole company.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
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]
American Heritage Idioms