Charles Ellicott Commentary Genesis 19:37-38

"And the first-born bare a son, and called his name Moab: the same is the father of the Moabites unto this day. And the younger, she also bare a son, and called his name Ben-ammi: the same is the father of the children of Ammon unto this day." — Genesis 19:37-38 (ASV)

Moab ... Ben-ammi. — Both these names suggest an incestuous origin, but the latter in a less repulsive way. “Son of my people” means one born of intercourse with her own kin and family. It is a striking proof of the vigor of the race of Terah that, from this lone cavern and after the loss of all the wealth Lot possessed, these two children were able to subdue the original inhabitants dwelling on the eastern shore of the Dead Sea and establish small kingdoms there. Both Moabites and Ammonites have finally merged with the Arabs.