Why is Joshua called "Jesus" in Hebrews 4:8 in the KJV?

"For if Joshua" (not "Jesus," it is simply the Greek form of the word) "if Joshua had given them rest," (that is, when he brought them into the land of Canaan) "then would he not have spoken of another day."

There are two parts of the New Testament which follow the Septuagint exactly, even where this differs decidedly from the Hebrew. These two parts are the speech of Stephen, recorded in Acts 7, and the Epistle to the Hebrews. In both of these documents we are certain that we are reading the words of men who had the Septuagint translation, and not the Hebrew original, in their hands. Stephen, we know, was a deacon of the Grecians (i.e. of the Hellenists — the very community which produced this version). And there are unmistakable marks, in the Epistle to the Hebrews, of its having been written by a native of Alexandria, the birth-place of the Septuagint. Now, in each of these two documents, the name Jesus occurs in rather an embarrassing manner. In Stephen's speech, we are told of the "tabernacle of witness, which our fathers brought in with Jesus into the possession of the Gentiles." And in the Hebrews 4, we read, "If Jesus had given them rest" In both of these places it is Joshua that is meant, of which name Jesus is only the Greek form, and is the form always used in the Septuagint.

The Greek form of Joshua, it occurs in Acts 7:45; Heb, 4:8, for Joshua the son of Nun.

Je’sus - Greek form of Jehoshua

This will be very clearly seen by a consideration of the meaning of the name Jesus, which Joseph was instructed to give to the Child when He should be born. As may be seen from Hebrews 4:8, Jesus is the Greek form of Joshua, or Jehoshua, which signifies "Jehovah is salvation," or "whose salvation is Jehovah." There is therefore ample justification for the common observation that the name Jesus means Jehovah the Saviour. If so, what a subject for contemplation, yea, and for adoration, is thus brought before our souls! A child born into the world, of lowly parentage in man's esteem, is declared, divinely declared, to be Jehovah the Saviour! Yes, the God who heard the groaning of His people Israel in Egypt, who saw their affliction, heard their cry by reason of their taskmasters, knew their sorrows, and came down to redeem them out of Egypt, and to bring them up out of that land unto a good land and a large, unto a land flowing with milk and honey; He who said unto Moses, "I am JEHOVAH: and I appeared unto Abraham, unto Isaac, and unto Jacob, by [the name of] God Almighty, but by My name JEHOVAH was I not known to them" (Ex. 3:6-8; Ex. 6:2-3); it was He, the same God, the same Jehovah, the El Shaddai known to the patriarchs, who now came into this world as a Babe. But if a Babe, He came, blessed be His name for ever, as the Saviour of His people. Surely we may say that the shadows were fleeing away, and that the darkness, which had hitherto shrouded God from His people, was fast disappearing. It was indeed the blessed dawn of the day of grace.

This will be very clearly seen by a consideration of the meaning of the name Jesus, which Joseph was instructed to give to the Child when He should be born. As may be seen from Hebrews 4:8, Jesus is the Greek form of Joshua, or Jehoshua, which signifies "Jehovah is salvation," or "whose salvation is Jehovah." There is therefore ample justification for the common observation that the name Jesus means Jehovah the Saviour. But if so, what a subject for contemplation, yea, and for adoration, is thus brought before our souls! A child born into the world, of lowly parentage in man's esteem, is declared, divinely declared, to be Jehovah the Saviour! Yes, the God who heard the groaning of His people Israel in Egypt, who saw their affliction, heard their cry by reason of their taskmasters, knew their sorrows, and came down to redeem them out of Egypt, and to bring them up out of that land unto a good land and large, unto a land flowing with milk and honey; He who said unto Moses, "I am JEHOVAH: and I appeared unto Abraham, unto Isaac, and unto Jacob, by [the name of] God Almighty, but by My name JEHOVAH was I not known to them" (Exodus 3:6-8; 6:2-3); it was He, the same God, the same Jehovah, the El Shaddai known to the patriarchs, who now came into this world as a Babe. But if a Babe, He came, blessed be His name for ever, as the Saviour of His people. Surely we may say that the shadows were fleeing away, and that the darkness which had hitherto shrouded God from His people was fast disappearing. It was indeed the blessed dawn of the day of grace.

Josh’u a - same as Jehoshua

Joshua means "Jehovah is Saviour"; the Greek name for Joshua is Jesus. In our study of the previous books, beginning with Exodus, we have met his name at different times and have learned much of this great man of God. He was the Son of Nun, an Ephraimite (Num. 13:8), grandson of Elishama (1 Chron. 7:26-27). In Exodus we saw him as the leader of Israel against Amalek. He is mentioned as Moses' servant and attendant (Ex. 24:13; 32:17-18); as the servant of Moses, he did not depart out of the tabernacle (Ex. 33:11). He went with Moses, up into the mount of God.

The meaning of the name of "Jesus" is deep — "Jehovah a Saviour," and faith lays hold of those glories as being His: personally JEHOVAH, — in action, the SAVIOUR. Yet the name (as we see in Acts 7:45, and Heb. 4:8) was a name not uncommon among the Jews, but rather one of their national ones — "Joshua."

*And as to Moses and Joshua, I would further observe this — that they performed very different services for Israel, and they set forth the Lord in very different characters. Moses was the mediator between God and the people while travelling through the wilderness; Joshua was the saviour of the people out of the wilderness, and their leader into the land of rest and promise. Moses, therefore, presents the Lord in His Priesthood, or Mediatorship, as in this dispensation, or, as with the church. Joshua presents Him to us in His character as Saviour of Israel in the latter day, when He shall lead His ransomed tribes into their promised rest. Jesus is Saviour and Jesus and Joshua are one — the former being the Greek, the latter the Hebrew, form of the very same name.