Definition of "all in"

By half past seven we were both pretty nearly all in, and wet from innumerable fordings of the river, so we stopped and boiled some hot water with the sugar left over from lunch.

1927 November 10, Aldo Leopold, “Part 2, Country: The Gila, 1927”, in Round River: From the Journals of Aldo Leopold, New York: Oxford University Press, published 1953

Either the celebrated lilt of her voice was born in, or she had used it so much and so long that it might as well have been. She looked all in, no doubt of that, but the lilt was there.

1955, Rex Stout, “The Next Witness”, in Three Witnesses, Bantam edition, Viking Press, published Oct 1994, page 51