Heidegger's Bible Handbook: Joshua: Its Title
1. The name of the book. Joshua, whence his name, and who was he?
This book is called יהשע/Yehoshua/Joshua, Ἰησοῦς/Jesus by the Septuagint translators, which means Savior; it is thus named because it contains the eminent works, life and death of Joshua, the son of Nun, called Ναυῆ/Nave by the Greeks, born in Egypt of the tribe of Ephraim, the attendant of Moses, one of the number of Spies sent from Rephidim into Canaan, and, because of the faithfulness in that legation rendered to God, Moses, and the faithful people, the divinely designated the successor of Moses and Leader of the people as the primary character of this drama.
 See Numbers 13.