A reconvergence of what the day scattered
Sappho was a Greek lyric poet, born on the island of Lesbos. The Alexandrians included her in the list of nine lyric poets. Her birth was sometime between 630 and 612 BCE, and it is said that she died around 570 BCE, but little is known for certain about her life. The bulk of her poetry, which was well-known and greatly admired through much of antiquity, has been lost, but her immense reputation has endured through surviving fragments.
Pynchon is referencing this Sappho poem:
To EveningThou bring'st the child, too, to his mother's side.
O HESPERUS! Thou bringest all things home;
All that the garish day hath scattered wide;
The sheep, the goat, back to the welcome fold;