Kepha/Cephas is a name associated with the high priest. In fact, that is where the name of the wicked high priest, Caiaphas, comes from.Now the names of the twelve apostles are these: The first, Simon, who is called Peter, and Andrew his brother; James the son of Zebedee, and John his brother; (ASV, Matthew 10:2)
Peter’s original name, according to the Greek text is Simon son of Jonah (John 21:15). However, being a Jew, his Hebrew name would have been שמעון בן יונה (shimon ben yonah). The name שמעון (shimon, Strong's #559) means "heard." In Mark 3:16 we are told that Yeshua (Jesus) gives Shimon the name Peter (Petros in Greek), a Greek name that has no equivalency in Hebrew. However, in John 1:42 we are told that his new name is, according to the Greek, Kephas (Cephas), not Petros (Peter). Kephas is a Greek transliteration of the Aramaic name כאפא (Kepha, pronounced kee-phah) meaning "stone."
And I tell you, that you are Kepha, and upon this rock (kepha) I will build my assembly. (Matthew 16:18 from the Peshitta, a 4th Century Aramaic New Testament) ~ Jeff Benner, https://www.ancient-hebrew.org/names/Peter.htm
I wonder if it has anything to do with 1 Peter 2:5? you also, like living stones, are being built into a spiritual house to be a holy priesthood, offering spiritual sacrifices acceptable to God through Jesus Christ.