פּירוש אויף דברים 2:11

רפאים יחשבו וגו׳ THEY [ALSO] ARE ACCOUNTED REPHAIM, [AS THE ANAKIM] — As Rephaim are those Emim accounted, even as the Anakim — who are also termed Rephaim because the hands of everyone who beheld them became weak (רפה) (cf. Genesis Rabbah 26:7).

רפאים יחשבו אף הם כענקים, “the Refaim were also considered as part of a race of giants.” They were considered as such not because of their height, but because of their physical strength. That they were not truly giants is clear from the fact that the Moabites called them Eymim. This was the name by which most people called them.

I have already given the etymology of the name Refaim [comment on Genesis 14: 5].

אמים — so called because the dread (אימה) of them lay upon the people. — So, too, (v. 12) the Horim dwelt formerly in Seir and I gave them over unto the children of Esau. (Genesis Rabbah 26:7)