Albert Barnes Commentary 2 Chronicles 20:1

"And it came to pass after this, that the children of Moab, and the children of Ammon, and with them some of the Ammonites, came against Jehoshaphat to battle." — 2 Chronicles 20:1 (ASV)

The present Hebrew (and English) text mentions the Ammonites twice. Therefore, some adopt a different reading and translate, “the children of Ammon, and with them certain of the Maonites,” etc. Compare the notes on 2 Chronicles 20:10, Judges 10:12, and 1 Chronicles 4:41.