For over 300 years, from the days of Nephi to the days of King Mosiah 1st, there had been continual wars between the Nephites and the Lamanites (2 Nephi 5:34; Omni 1:10). During that time the Nephites had been “scattered upon much of the face of the land” (Jarom 1:6), and by 279 BC “the more wicked part of the Nephites were destroyed” (Omni 1:5). In the early days of King Mosiah 1st the more righteous surviving Nephites were living in a city called Lehi-Nephi (Omni 1:12, 27; Mosiah 7:1, 4).
The name of this city is interesting because it is similar to the name that converted Lamanites took upon themselves in the days of Ammon. “And it came to pass that they called their names Anti-Nephi-Lehies; and they were called by this name and were no more called Lamanites” (Alma 23:17-18). It appears that they dropped the name of Lamanites to identify with their more righteous father, Lehi. The Anti-Nephi-Lehies were friendly with the Nephites and had correspondence and association with them (Alma 23:18).
The name of the city Lehi-Nephi indicates a similar situation where at the time the city was established it appears there would have been righteous Lamanites and Nephites living there in peace and harmony one with another. In the record of Zeniff we read that this was his desire when he led a company to return to the land of their fathers. He had been among the Lamanites in the land of Lehi-Nephi and saw there was much good among them (Mosiah 9:1). He went to the king of the Lamanites and asked if they could live among them and reclaim the land of Lehi-Nephi and the land of Shilom (Mosiah 9:6).
In the beginning of Zeniff’s record he refers to the “city of Lehi-Nephi” and how they began to build buildings and repair its walls (Mosiah 9:6, 9). In his record thirteen years later, with no explanation, Zeniff changes the name of the city Lehi-Nephi to the “city of Nephi” (Mosiah 9:15), and it is thereafter referred to as “the city of Nephi.” The probable reason for the name change lies in the events that occurred in that interval.
The Nephites were industrious farmers and herdsmen and King Laman planned from the beginning to allow the Nephites to settle in their midst so that the Lamanites might glut themselves on the labors of the Nephites (Mosiah 9:10-12). In the thirteenth year of their settlement king Laman began to execute his plan and to stir up his people to war and contention against the Nephites (Mosiah 9:13). Peace and harmony were gone and the name of the city of Lehi-Nephi no longer described the relationship between these people. The new circumstances demanded the name change to the “city of Nephi”.
I always figured the Anti-Nephi-Lehis assumed that name because that was the name of their well-beloved king.