English form of the name of the best-known of all Christ's apostles, traditionally regarded as the founder of the Christian Church. The name derives, via Latin, from Greek petros ‘stone, rock’. This is used as a translation of the Aramaic byname Cephas, given to the apostle Simon son of Jona, to distinguish him from another of the same name (Simon Zelotes). ‘When Jesus beheld him, he said, Thou art Simon the son of Jona: thou shalt be called Cephas, which is by interpretation, A stone’ (John 1:42). According to Matthew 16:17–18, Christ says more explicitly, ‘Blessed art thou, Simon Bar-jona … thou art Peter, and upon this rock I will build my church’. The name has been in continuous use since the Middle Ages.