Parashas Vayeira · Passuk 19:38
And the younger also bore a son and called his name Ben-Ammi; he is the father of the children of Ammon to this day.
Torah Temimah points to Nazir 23b (and parallel in Bava Kamma).
TT lemma: בן עמי.
English: “Ben-Ammi.” It was taught: Rabbi Chiyya bar Abba said in the name of Rabbi Yochanan: From where do we know that the Holy One, blessed be He, does not withhold even the reward for refined speech? The first-born, who named her son Moav (“from father”), was told concerning Moav, “Do not harass Moav and do not contend with them in war”—war is forbidden, but forced labor is permitted. The younger, who named her son Ben-Ammi (“son of my people”), was told, “Do not harass them and do not contend with them”—even forced labor is not to be imposed upon them.
Derash on the verse (Bavli sugya) — not a formal named middah of the 13. Refined versus crude speech is rewarded with graded protection.
Hashem does not withhold even the reward for refined speech: the younger daughter’s more modest name “Ben-Ammi” earned her descendants fuller protection than the franker name “Moav.”