Alma 3:11

And it came to pass that whosoever would not believe in the tradition of the Lamanites, but believed those records which were brought out of the land of Jerusalem, and also in the tradition of their fathers, which were correct, which believed in the commandments of God, and kept them, were called the Nephites, or the people of Nephi, from that time forth;

Whoever would not believe the traditions of the Lamanites, but believed the records from Jerusalem and the true traditions of their fathers, and believed in God’s commands and kept them, were called the Nephites, or the people of Nephi, from that time on.

On the other hand, those who rejected Lamanite teachings and trusted the records brought from Jerusalem—who believed in the true traditions of their ancestors and kept God’s commands—they were called Nephites, the people of Nephi.