Charles Ellicott Commentary Deuteronomy 3:13

"and the rest of Gilead, and all Bashan, the kingdom of Og, gave I unto the half-tribe of Manasseh; all the region of Argob, even all Bashan. (The same is called the land of Rephaim." — Deuteronomy 3:13 (ASV)

The land of giants —i.e., of Rephaim.