Deuteronomy 2:10

The Emthanaia dwelt in it of old, a people great and many, and mighty as the giants.

Scripture informs us that the Moabites took Ar from the Emim (I have already given the etymology of the name Emim [comment on Genesis 14: 5]).

THE EMIM ABODE THEREIN FORMERLY etc. “You [Moses] might think that this is the land of the Rephaim which I gave to Abraham because the Emim, who are Rephaim, dwelled there formerly, but this [the land of the Moabites] is not the land [that I promised to Abraham], because I drove out those Rephaim from before the children of Lot and settled them in place of the Rephaim. Those Emim were considered Rephaim, (giants).” This is interpreted by Rashi to mean: “The Emim who formerly lived in the lands of Ammon and Moab were accounted as Rephaim, that is, the Anakim, (giants). But those lands of Ammon and Moab were not the land of the Rephaim which I promised to Abraham.” Therefore Moses was not to wage war against the lands of Ammon and Moab. like Anakim (giants) who are called Rephaim [from the root raphoh — weak] because the hands of everyone who sees them become ‘weak.’ Emim [from the root eimah — fear] are so called because their ‘dread’ lays upon people.” This is Rashi’s language. And similarly he wrote [further, in connection with the land of Ammon of which Scripture states], That also is accounted a land of Rephaim: “because the Rephaim dwelled there formerly, but that [land] is not what I gave to Abraham.”
But I wonder at the words of the Rabbi! Why should Scripture explain to us concerning the land of Ammon and Moab that it is not the land of Rephaim which He gave to Abraham? Was it to state that it was not due to Israel and was not part of the land which G-d swore to their fathers to give them? [That could not be the reason! On the contrary,] Scripture states only, because I have given it unto the children of Lot for a possession meaning that, although it was part of Abraham’s inheritance, the Holy One, blessed be He, gave it to the children of Lot for Abraham’s sake. As Rashi himself wrote: “[The lands of] two nations [from among the ten nations originally given to Abraham — Genesis 15:19-21], I gave to the children of Lot [Ammon and Moab] as a reward because Lot went with Abraham to Egypt and kept silent concerning what Abraham said about his wife, ‘she is my sister.’” Moreover, the Rabbi himself wrote with reference to Esau: “[The lands of] ten nations, 15:19-21: the Kenite, and the Kenizzite, and the Kadmonite; and the Hittite, and the Perizzite, and the Rephaim; and the Amorite, and the Canaanite, and the Girgashite, and the Jebusite. I gave to Abraham. …

האימים לפנים, seeing that the descendants of Lot had no legal claim to inherit anything from Avraham at all, G’d announced that He had given them ancestral land just as He had done to the descendants of Esau who were descended from Avraham in a straight line. G’d testifies that both the Ammonites and the Moabites came to possess what they owned contrary to accepted norms.