What does Genesis 35:21 mean?

This is the first time Scripture directly uses the name Israel for the man born as Jacob (Genesis 35:10). The two names will alternate throughout the rest of the Bible. His birth name of Ya'aqōb can suggest someone who "usurps," or steals the benefits of others. This is exactly what he did to his older twin, Esau (Genesis 25:25–26; 27:30–35). After a divine encounter with God, Jacob is given the name Yisrā'ēl, noting his struggling with both men and with the Lord (Genesis 32:28).

Jacob's beloved wife, Rachel, has recently died in childbirth (Genesis 35:16–20). The family was on their way from Bethel to the region of Ephrath (Genesis 35:1). Now they move on and set up camp at a location called Migdal-'ēder. This Hebrew phrase literally means "tower of the flock." It might have been an actual, literal watchtower meant to better observe the shepherds in the region. Or, this is simply the same given to that area. An exact location is unknown, though it's somewhere between Bethlehem (Genesis 35:19) and Hebron (Genesis 35:27).