stiff upper lip

Of American origin; the earliest known use is in 1811.https://www.google.co.uk/books/edition/The_Olive_Branch_Or_Faults_on_Both_Sides/vG89AAAAYAAJ?hl=en&gbpv=1&dq=stiff+upper+lip&pg=PA237&printsec=frontcover

• "I thought now the jig was mighty nigh up with me, but I determined to keep a stiff upper lip."
• "Stiff upper lip, stout fella. Carry on, old fluff. Chin up, keep muddling through. Stiff upper lip, stout fella, when the going’s rough. Pip pip to old man trouble and a toodle-oo too.[…] Stiff upper lip, stout fella, when you’re in the stew. Sober or blotto, this is your motto. Keep muddling through."
• "[...] Jeeves came in, bowler hat in hand, to say goodbye. A solemn moment, taxing our self-control to the utmost. However, we both kept the upper lip stiff, and after we had kidded back and forth for a while he started to withdraw. [...] He poked his head round the tree as I arrived, and when I waved a cheery hand at him, waved a fairly cheery hand at me. Though I only caught a glimpse of him, I could see that his upper lip was stiff."
• "In typical British stiff upper lip fashion, the tournament organizers expected us to play into, and through, the menacing weather."

• mustn't grumble