keep one's hair on

Verb

 * 1)  To stay calm; to be patient; to calm down.
 * All right, all right, just keep your hair on, mate.
 * 1) * 1965 [Chatto & Windus],, , 2016, (Vintage), page 138,
 * ‘Keep your hair on, I don't see any crime.’
 * ‘Keep your hair on, I don't see any crime.’

Usage notes
Chiefly used in the imperative mood.

Translations

 * German: halt / halte mal die Luft an, mach mal halblang