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Etymology

In the story of the calling of the disciples, Jesus addresses Simon Peter with the Greek term Κηφᾶς (Cephas), a Hellenised form of Aramaic ܟ݁ܺܐܦ݂ܳܐ (keepa), which means "rock", a term that before was not used as a proper name:

:ἐμβλέψας αὐτῷ ὁ Ἰησοῦς εἶπεν Σὺ εἶ Σίμων ὁ υἱὸς Ἰωάννου, σὺ κληθήσῃ Κηφᾶς ὃ ἑρμηνεύεται Πέτρος.

Jesus later alludes to this nickname after Peter declares Jesus to be the Messiah:

:κἀγὼ δέ σοι λέγω ὅτι σὺ εἶ Πέτρος καὶ ἐπὶ ταύτῃ τῇ πέτρᾳ οἰκοδομήσω μου τὴν ἐκκλησίαν, καὶ πύλαι ᾅδου οὐ κατισχύσουσιν αὐτῆς.

The Peshitta Syriac version renders Jesus' words into Aramaic as follows:

:ܐܳܦ݂ ܐܶܢܳܐ ܐܳܡܰܪ ܐ݈ܢܳܐ ܠܳܟ݂ ܕ݁ܰܐܢ݈ܬ݁ ܗ݈ܽܘ ܟ݁ܺܐܦ݂ܳܐ ܘܥܰܠ ܗܳܕ݂ܶܐ ܟ݁ܺܐܦ݂ܳܐ ܐܶܒ݂ܢܶܝܗ ܠܥܺܕ݈݁ܬ݁ܝ ܘܬ݂ܰܪܥܶܐ ܕ݁ܰܫܝܽܘܠ ܠܳܐ ܢܶܚܣܢܽܘܢܳܗ܂

Paul of Tarsus later uses the appellation Cephas in reference to Peter.