Keep your hair on

Usually Used to tell somebody to not go on about something

Daniel: MATILDA WHAT DID YOU DO TO MY NINTENDO SWITCH YOU THREW IT OUT THE WINDOW YOU WANKER

Matilda: Gee Keep Your Hair on

Daniel: My Hair is on thank you
Matilda: It’s a saying Dufus duh it’s not like something I’ve made up
Dainel: You are such a Wankstain
Matilda: Fuck you Cum

keep your hair on

to request someone to stay calm and not get annoyed

The general said keep your hair on during the meeting this time