Nimrim is mentioned twice in scripture in the Tanakh and Holy Bible. First in the Book of Isaiah (15:6), and in the Book of Jeremiah (48:34). Little is known of Nimrim other than it was in Moab because it's mentioned in connection with several cities that were under Moabite control at that time (around 626BC - 586BC) such as, Heshbon, Zoar (previously known as, Bela (Genesis 14:8) and Horonaim. Scholars are not in agreement of whether Nimrim was a river, or a lake, or a city.
References
Nimrim Wikipedia(Text) CC BY-SA