What are the earliest references to a Priest being referred to as “Father”?
St Paul in some of the Epistles calls himself a ‘father’ to those whom he has taught, so I guess it dates right back to the very beginning.
I would agree with that.
Jesus gives the keys to Peter in Matthew 16:18-19. Jesus phrasing is a direct reference to Isaiah 22:20-23 where Eliakim is made head of the household and operates as the prime minister of the King. In the passage it is said that he will be “a father to the people.”
Peter is our first Pope. Pope means papa. Peter was made the prime minister and would be a father to the people of God. The practice of a priest being called father actually started with Jesus himself. It is for this reason that Paul was comfortable referring to himself as a father in the faith.