Jesus is THE ROCK, the Petra, Peter is one of the stones, the petros.
These are greek terms. Greek was the language of commerce in first century Palestine. Jesus and Peter spoke the everyday language of Aramaic.
Jesus referred to Peter IN HEBREW as "Kepha" which was translated directly into Greek as "petra." When translated as a name it was rendered "Petros" because of grammatical gender: "petra" in Greek is feminine, while Peter's name had to be given as the masculine "Petros."