What was Joshua son of Nun called before Moses renamed him?

Answer: Hoshea

Hoshea son of Nun was the spy from the tribe of Ephraim, and Moses gave him the name Joshua.

“from the tribe of Ephraim, Hoshea son of Nun; These were the names of the men Moses sent to spy out the land; and Moses gave to Hoshea son of Nun the name Joshua.”— Numbers 13:8, 13:16 (BSB)