Ammon in Fausset's Bible Dictionary

A nation sprung from Ben-ammi, Lot's son by his younger daughter (Genesis 19:38; Psalm 83:7-8), as Moab by his elder, after Lot escaped from Sodom. Ammon and Moab appear continually together; both are said to have hired Balaam (Deuteronomy 13:4), though Moab alone is mentioned in the detailed account (Numbers 22; 23). The land from Arnon river to Jabbok is assigned to both (Judges 11:12-18; Judges 11:25). The Israelites dispossessed the Amorites of land which afterward Ammon occupied, between Arnon and Jabbok, but did not, as Jephthah reasons, dispossess Ammon of it, though now claiming it as theirs (Numbers 21:24; Numbers 21:26; Numbers 21:29). Ammon destroyed the aboriginal Rephaim or giants, named Zamzummim, and occupied their land, Jabbok being their boundary (Deuteronomy 2:20-21; Deuteronomy 2:37)...

Link: https://bible-history.com/faussets/A/Ammon/