What is the meaning of "Musabos Shem"?
Rashi: It means that, since Nevo and Ba'al Me'on were named after idolatry - the B'nei Reuven changed their names. 1
Da'as Zekenim and Hadar Zekenim: They were initially named by Amon and Mo'av, and later by Sichon, and in the end, by Yisrael.
Targum Onkelos and Targum Yonasan: They changed the names of the towns that they captured 2 and rebuilt to the names of those who rebuilt them. 3
See also Targum Yonasan and Na'ar Yonasan.
It is not clear however, as to why, in Pasuk 21 & 42, the Torah writes this with regard to Ya'ir and Novach, respectively, and does not mention it with regard to Machir? See Na'ar Yonasan.
Which were originaly named after those who built them. See Na'ar Yonasan.
Rashi - in Vezos ha'Berachah Devarim, 33:21 - writes that Gad chose the place in which Moshe would be buried. But he died on Har N'vo and was buried there, and Har N'vo was in Reuven's territory?
R. Chaim Paltiel (in Devarim 33:21, citing Sotah 13b): Although Moshe died on Har N'vo 1 , he was buried in the valley 2 below, 3 which was in the territory of Gad.
As the Torah testifies in Devarim, 34:1 & 5 "Vaya'al... el Har Nevo ... Vayamas Sham".
As the Torah writes there in 34:6 "Vayikvor oso ba'Gai".
Sotah 14a: To someone who stood on top of the mountain, he appeared to be buried in the valley, and to someone who stood in the valley, he appeared to be buried on top of the mountain..