I had thought the title of the book and movie were from something that I recognized, but I didn’t figure it out until I came across this snippet of poetry:

That is no country for old men. The young
in one another’s arms, birds in the trees
- Those dying generations - at their song,
Fish, flesh, or fowl, commend all summer long
Whatever is begotten, born, and dies.
– W. B. Yeats, Byzantium