Genesis 19:36-38

Amplified Bible

³⁶ Thus both the daughters of Lot conceived by their father. ³⁷ The firstborn gave birth to a son, and named him Moab (from father); he is the father of the Moabites to this day. ³⁸ The younger also gave birth to a son and named him Ben-ammi (son of my people); he is the father of the Ammonites to this day.