אֶֽרֶץ־רְפָאִ֥ים תֵּחָשֵׁ֖ב אַף־הִ֑וא רְפָאִ֤ים יָֽשְׁבוּ־בָהּ֙ לְפָנִ֔ים וְהָֽעַמֹּנִ֔ים יִקְרְא֥וּ לָהֶ֖ם זַמְזֻמִּֽים׃
(Por tierra de gigantes fué también ella tenida: habitaron en ella gigantes en otro tiempo, á los cuales los Ammonitas llamaban Zomzommeos;
Rashi
ארץ רפאים תחשב IT (AMMON) ALSO WAS ACCOUNTED A LAND OF REPHAIM. — It also is accounted a land of Rephaim because the Rephaim formerly dwelt in it, but yet it is not that land which I gave to Abraham.
Chizkuni
ארץ רפאים תחשב אף היא, “that land was also considered as land of the Refaim.” It was considered “as if,” but in fact was not. They were really Zamzumim, because they were always implicated in a war or in the planning of a war.
Ibn Ezra
The word Zamzummim is inflected according to the rules of the Hebrew language into which it has been assimilated. Compare, “the satraps” [Esther 8: 9].