Why did Jesus name Simon as Peter the rock?

God often changes people's names when He has a very special mission for them. And their new name is indicative of what He intends for them. Abram became Abraham, the father of nations, Jacob became Israel, etc. Peter is the Anglo form of Petros, which is the Greek form of Kephas, which is the Hebrew Word for rock. Before this particular name change, none of them: Peter, Petros, or Kephas or Cephas were personal names, they only became such when Our Blessed Lord changed Simon's name to Cephas. Obviously Our Blessed Lord was naming Peter as the firm foundation on which He was going to built His Church in St. Matthew's Gospel 16:17-19. This has a direct parallel in the Old Testament book of Isaiah 22:15-25 when the Lord disposed Sobna and appointed Eliacim as the Vicar of the Davidic King. In St. Matthew's Gospel, Our Blessed Lord is appointing Peter as His Vicar to rule the Church in his stead, just exactly as the Vicar or Prime Minister ruled the kingdom of Israel in the King's name.