Question about Joshua 24:2

[Swammerdami]

Following is a longish excerpt from Chapter 24 of the Book of Joshua. My question is about verse 2 specifically (but I quote several more verses from Our Orange Fuhrer's second-favorite book to summarize ancient Jewish history, and out of deference to our beloved Fuhrer whose wisdom is not to be questioned, and to celebrate His endorsement of Israeli conquests in progress).

The translation shown here is the New Century Version, but the relevant place-name -- shown in red -- is the same in several other translations. The alternate shown for the King James Version also appears in several translations.

2 Then Joshua said to all the people, “Here’s what the Lord, the God of Israel, says to you: ‘A long time ago your ancestors lived on the other side of the Euphrates River. Terah, the father of Abraham and Nahor, worshiped other gods.

2 And Joshua said unto all the people, Thus saith the Lord God of Israel, Your fathers dwelt on the other side of the flood in old time, even Terah, the father of Abraham, and the father of Nachor: and they served other gods.

2 Y’hoshua said to all the people, “This is what Adonai the God of Isra’el says: ‘In antiquity your ancestors lived on the other side of the [Euphrates] River — Terach the father of Avraham and Nachor — and they served other gods.

3 But I, the Lord, took your ancestor Abraham from the other side of the river and led him through the land of Canaan. And I gave him many children, including his son Isaac. 4 I gave Isaac two sons named Jacob and Esau. I gave the land around the mountains of Edom to Esau, but Jacob and his sons went down to Egypt. 5 Then I sent Moses and Aaron to Egypt, where I brought many disasters on the Egyptians. Afterwards I brought you out. 6 When I brought your ancestors out of Egypt, they came to the Red Sea, and the Egyptians chased them with chariots and men on horses. 7 So the people called out to the Lord. And I brought darkness between you and the Egyptians and made the sea to cover them. You yourselves saw what I did to the army of Egypt. After that, you lived in the desert for a long time.

8 “‘Then I brought you to the land of the Amorites, east of the Jordan River. They fought against you, but I handed them over to you. I destroyed them before you, and you took control of that land. 9 But the king of Moab, Balak son of Zippor, prepared to fight against the Israelites. The king sent for Balaam son of Beor to curse you, 10 but I refused to listen to Balaam. So he asked for good things to happen to you! I saved you and brought you out of his power.

11 “‘Then you crossed the Jordan River and came to Jericho, where the people of Jericho fought against you. Also, the Amorites, Perizzites, Canaanites, Hittites, Girgashites, Hivites, and Jebusites fought against you. But I handed them over to you. 12 I sent terror ahead of you to force out two Amorite kings. You took the land without using swords and bows. 13 I gave you that land where you did not have to work. I gave you cities that you did not have to build. And now you live in that land and in those cities, and you eat from vineyards and olive trees that you did not plant.’”

It's easy to understand wording or spelling variations between translations, but why would a proper name sometimes appear and sometimes not? The Complete Jewish Bible, with "Euphrates" shown in brackets, probably implies the answer: Some ancient editor deduced that an unnamed river was the Euphrates. Deduced how? Process of elimination?

The issue has relevance because elsewhere we learn that Terah and Abraham came from "Ur of the Chaldees" (Ur of the Kasdim) which is usually identified as the Sumerian city of Ur which is to the West of the Euphrates, and hence NOT on the "other side" of that river. There are several other problems with that identification: Terah's family appear to have traveled south while Canaan is to the north of Sumerian Ur. "Chaldees" is equated to "Chaldeans", a people who first appear in lower Mesopotamia many centuries after the alleged time of Abraham.