The Pope is the Vicar of Christ
A vicar is a representative, substitute; anyone acting "in the person of" or agent for a superior.
“For thou art the shepherd, thou art the physician, thou art the director, thou art the husbandman, finally thou art another God on earth.” From one of the Councils; Labbe and Cossart’s “History of the Councils.” Vol. XIV, col. 109
Pope John XXII
The title “Lord God the Pope” is found within a gloss of Extravagantes of Pope John XXII, title 14, chapter 4
In an Antwerp edition of the Extravagantes, the words, ”Dominum Deum Nostrum Papam” (Our Lord God the Pope) can be found in column 153. In a Paris edition, they are found in column 140.
Pope Bonifatius VIII
The Bull Unam Sanctam… Issued by POPE BONIFACE VIII reads as follows:
”The Roman Pontiff judges all men, but is judged by no one. We declare, assert, define and pronounce: to be subject to the Roman Pontiff is to every human creature necessary for salvation that which was spoken of Christ ‘thou has subdued all things under his feet’ may well seem verified in me… I have the authority of the King of Kings. I am all in all and above all, so that God himself and I, the vicar of God, have but one consistory, and I am able to do all that God can do.”
Pope John XXIII
“The Saviour Himself is the door of the sheepfold: ‘I am the door of the sheep.’ Into this fold of Jesus Christ, no man may enter unless he be led by the Sovereign Pontiff; and only if they be united to him can men be saved, for the Roman Pontiff is the Vicar of Christ and His personal representative on earth.” (Pope John XXIII in his homily to the Bishops and faithful assisting at his coronation on November 4, 1958).
‘VICARIUS FILII DEI’. which is the Latin for ‘VICAR OF THE SON OF GOD.’