"And she called his name Moab" (Genesis 19:37-38). Rabbi Chiya bar Abba said in the name of Rabbi Yochanan: the Holy One, blessed be He, does not withhold the reward even for refined speech. For whereas the firstborn, who said "Moab" [meaning "from father"], openly naming the disgrace - the Holy One, blessed be He, said to Moses, "Do not provoke them to war" (Deuteronomy 2:9). War He forbade, but He did permit forced labor to be imposed upon them. But the younger daughter, who said "Ben-Ammi" ["son of my people," discreetly] - the Holy One, blessed be He, said to Moses, "and when you draw near opposite the children of Ammon, do not harass them and do not provoke them" (Deuteronomy 2:19), [meaning] that you may not even impose forced labor upon them.
God Repays Even a Modest Turn of Phrase
Yalkut Shimoni on Torah 86:7
(בראשית יט לז-לח) וַתִּקְרָא אֶת שְׁמוֹ מוֹאָב. אָמַר רַבִּי חִיָּא בַּר אַבָּא אָמַר רַבִּי יוֹחָנָן, אֵין הַקָּדוֹשׁ בָּרוּךְ הוּא מְקַפֵּחַ אֲפִלּוּ שְׂכַר שִׂיחָה נָאָה דְּאִלּוּ בְּכִירָה דְּקָאָמְרָה מוֹאָב מִן אָב, אָמַר הַקָּדוֹשׁ בָּרוּךְ הוּא לְמֹשֶׁה, "אַל תִּתְגָּר בָּם מִלְחָמָה". מִלְחָמָה הוּא דְּלֹא הָא אַנַגְרַיָא עָבִיד בְּהוּ, וְאִלּוּ צְעִירָה דְּקָאָמְרָה בֶּן עַמִּי אָמַר הַקָּדוֹשׁ בָּרוּךְ הוּא לְמֹשֶׁה, (שם יט) "וְקָרַבְתָּ מוּל בְּנֵי עַמּוֹן אַל תְּצֻרֵם וְאַל תִּתְגָּר בָּם" "דְּאֲפִלּוּ אַנַגְרַיָא לֹא תַּעֲבִיד בְּהוּ.