ציטירנדיקער פּירוש אויף יהושע 9:10

<p>"Ataroth and Dibon": From the land of Sihon and Og they were. It appears that Rashi believed that the land of Midian was not divided among the tribes, and therefore he wrote "from the land of Sihon and Og they were." Similarly, in the Book of Joshua, you will not find that the land of Midian was divided at all. Perhaps this was because it was not considered part of the land of Israel, i.e., from the seven nations.
"And Nebo and Baal-meon": The names were those of idolatry, etc. It is difficult to know how Rashi knew this. One could say that since it is written elsewhere, "Kiryat Baal, that is, Kiriath-jearim" (Joshua 9:10), and it is mentioned as "Baal" and "Nebo" where idolatry is evident (as the names of the deities), it is clear that Baal and Nebo were idolatrous names. Since it says "Nebo and Baal-meon" in the same context, it implies that they alone were named after idols and not others. Later, it states "and Sibmah," which implies that their names were not changed as mentioned earlier, but rather, it retained its original name.</p>