
Check out the Children's Book of Mormon Stories book published by LDS Inc.
Specifically Chapter 9: A New Home in the Promised Land,” Book of Mormon Stories, 25
Towards the bottom of the page:

Laman and Lemuel’s followers called themselves Lamanites.
They became a dark-skinned people.
God cursed them because of their wickedness.

The Lamanites became lazy and would not work.

The people who followed Nephi called themselves Nephites.
The Lamanites hated the Nephites and wanted to kill them.