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]

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