keep one's shirt on Idiom
keep one's shirt on|keep|shirt
v. phr.,
slang To calm down; keep from losing your temper or getting impatient or excited.
Bob got very angry when John accidentally bumped into him, but John told him to keep his shirt on. 
Usually used as a command; may be considered impolite.
John said to Bob, "Keep your shirt on." Antonym: GET ONE'S DANDER UP.
keep one's shirt on
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]
keep (one's) shirt on
To abide calm and delay for something. Typically acclimated as an acute in the byword "keep your shirt on." Keep your shirt on, dude, the pizza will be actuality anon enough. It would accept gone calmly if Larry had been able to accumulate his shirt on instead of aggravating to get in early.Learn more: keep, on, shirtkeep one's shirt on
Stay calm, be patient; not accord way to atmosphere or excitement. For example, Keep your shirt on, Bob, they'll be actuality in time for the wedding. [Colloquial; mid-1800s] Learn more: keep, on, shirt