Deuteronomy 2:20 Midrash

אֶֽרֶץ־רְפָאִ֥ים תֵּחָשֵׁ֖ב אַף־הִ֑וא רְפָאִ֤ים יָֽשְׁבוּ־בָהּ֙ לְפָנִ֔ים וְהָֽעַמֹּנִ֔ים יִקְרְא֥וּ לָהֶ֖ם זַמְזֻמִּֽים׃

That also is accounted a land of Rephaim: Rephaim dwelt therein aforetime; but the Ammonites call them Zamzummim,

Read midrashic interpretation of Deuteronomy 2:20: and classical rabbinic exegesis.