Definition of "bourne"

But that the dread of something after death, / The undiscover'd country from whose bourn[e] / No traveller returns

c. 1599–1602, William Shakespeare, Hamlet, act 3, scene 1

[…] and though I did not stop in my advance, yet I went on slowly, like a man who should have passed a bourne unnoticed, and strayed into the country of the dead.

1879, Robert Louis Stevenson, Travels with a Donkey in the Cévennes

For though from out our bourne of Time and Place,The flood may bear me far,I hope to see my Pilot face to faceWhen I have crossed the bar.

1889, Alfred Tennyson, Crossing the Bar