LXX Gen 50:11

καὶ ἴδον οἱ κάτοικοι τῆς γῆς Χανάαν τὸ πένθος ἐν ἅλωνι Ἀτὰδ καὶ εἶπαν Πένθος μέγα τοῦτό ἐστιν τοῖς Αἰγυπτίοις· διὰ τοῦτο ἐκάλεσεν τὸ ὄνομα αὐτοῦ Πένθος Αἰγύπτου, ὅ ἐστιν πέραν τοῦ Ἰορδάνου.

When the Canaanites of the land saw the mourning at the threshing floor of Atad, they said, “This is a solemn ceremony of mourning by the Egyptians.” Thus the place across the Jordan is called Abel-mizraim.