What is the significance of the names of the city?
Rashi: Kiryas Sefer refers to Halachos that were forgotten in the mourning over Moshe. 1 Osni'el ben Kenaz recovered them.
Radak: In Persian, Sefer is called Devir.
Malbim (Shoftim 1:11): Devir is called Kiryas Sneh (based on "Retzon Shochni Sneh"
Maharsha (Temurah 16a): Now the city was called "Devir"