What does the phrase “a stiff upper lip” mean and Where does it originate?

The phrase “a stiff upper lip” means courage, or stoicism, which one keeps or carries.

The significance of the idiom is well indicated by one of its earliest appearances in print, John Neal’s down Easters (1833):

“What’s the use of boohooin’? Keep a stiff upper lip; no bones broke, don’t I know?”