Where does “Sisnaajiní” come from?

Sisnaajiní (Navajo) comes from Navajo sis, from Proto-Athabaskan səx.

Ancestry of “Sisnaajiní”, step by step

Step	Language	Word	Meaning
1	Navajo	sis	belt, sash, girdle; hill, mountain
2	Proto-Athabaskan	səx	—