On The Servant of the Servants of God
“When the Pope uses the title of servus servorum Dei, originally assumed by Pope St. Gregory the Great as a description of the power of the Supreme Keys, one must remember that the formula servus servorum is not a genitive of object, as if the pope were the one who serves the servants of God, but an hebraic genitive signifying a superlative sense as in saecula saeculorum, virgo virginum, caeli caelorum, and so on. The formula therefore means that the pope is the servant of God more than all the others, the servent of God par excellance, not that he is the servant of those who are the servants of God. Were it otherwise, the formula would tend to imply that the pope was the servant of men rather than of God, and would also imply that only the pope was not a servant of God, while everyone else was.”
Romano Amerio, Iota Unum, p. 150