keep one's hair on

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keep one's hair on (third-person singular simple present keeps one's hair on, present participle keeping one's hair on, simple past and past participle kept one's hair on)

1. (idiomatic, British, Ireland, colloquial) To stay calm; to be patient; to calm down.

   All right, all right, just keep your hair on, mate.

   • 1901, Louis Couperus, translated by Alexander Teixeira de Mattos, Small Souls:

     “Oh, nothing, nothing!”
     “Yes, there’s something. I mean to know!”
     “Keep your hair on; it’s nothing.”
     “Out with it!” cried Addie, scarlet with rage.
     And he flew at Jaap’s throat.

   • 1965 [Chatto & Windus], Margery Allingham, The Mind Readers, 2016, Penguin Random House (Vintage), page 138,

     ‘Keep your hair on, I don't see any crime. […] ’

   • 2014, Melvin Rea, The Island They Towed Away, AuthorHouse, page 233:

     “Sorry old chap—keep your hair on—but surely you knew just about everyone was siphoning off the odd bit, here and there?”

Chiefly used in the imperative mood.

• (to stay calm): keep one's knickers on, keep one's pants on, keep one's shirt on

• (antonym(s) of “to stay calm”): get one's bowels in an uproar, get one's knickers in a knot, get one's knickers in a twist