keep one's shirt on

keep (one's) shirt on

To remain calm and wait for something. Typically used as an imperative in the phrase "keep your shirt on." Keep your shirt on, dude, the pizza will be here soon enough. It would have gone smoothly if Larry had been able to keep his shirt on instead of trying to get in early.
See also: keep, on, shirt
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

keep one's shirt on

Stay calm, be patient; not give way to temper or excitement. For example, Keep your shirt on, Bob, they'll be here in time for the wedding. [Colloquial; mid-1800s]
See also: keep, on, shirt
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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