The phrase appears three times in Haliburton’s novel:
I had heerd tell of her afore; how she used to carry a stiff upper lip, and make him and the broomstick well acquainted together; and, says I, why do you put up with her tantrums
She was not a bad lookin piece of furniture neither, and its a proper pity sich a clever woman should carry such a stiff upper lip--she reminds me of our old minister Joshua Hopewell’s apple trees.
Why, Sir, that’s A.B’s; he was well to do in the world once, carried a stiff upper lip and keered for no one.
Thanks a lot, Dave, appreciated.
Looks like this other - perhaps original - meaning was more ‘uncaring, angry at the world in general’.
Slightly different from ‘resolute in the face of difficulty’, I would suggest.