I believe George Lucas came up with the name Jedi thru the name Jedidiah also. In the bible David had a son and they named him Solomon. God informed Nathan the prophet to name him Jedidiah. After his father died and he became king, God asked Solomon to ask him for whatever he wanted. He did not ask for wealth, long life, or defeat of his enemies; instead he asked for descernment in ruling over such a vast number of people.

God was pleased by what he asked for and he gave him WISDOM that no other was equal or better then, even to this day. Lucas knew this and made the association, and used the name Jedi, because their strength was suppose to be their wisdom.