וַיֵּ֤רֶד הָעֲמָלֵקִי֙ וְהַֽכְּנַעֲנִ֔י הַיֹּשֵׁ֖ב בָּהָ֣ר הַה֑וּא וַיַּכּ֥וּם וַֽיַּכְּת֖וּם עַד־הַֽחָרְמָֽה׃ (פ)
Then the Amalekite and the Canaanite, who dwelt in that hill-country, came down, and smote them and beat them down, even unto Hormah.
Rashi on Numbers
ויכתום AND COMPLETELY DISCOMFITED THEM — This word is the same in meaning as (Deuteronomy 9:21) “and I pounded it (ואכות) and ground it very thin”. The text implies: blow upon blow.
Sforno on Numbers
וירד העמלקי, and did not give them a chance to climb the mountain.
Siftei Chakhamim
To commemorate this incident. Meaning either that this was prophetic, or that Moshe used this name when he wrote down the Torah after forty years in the desert. By this time the place was already called Chormah.