This is a Greek abbreviation of the title, “Christ”.
“Chi” and “Rho” are the first two letters in the Greek word Christos or “Christ”.
In Greek capital letters they appear as ” X” and “P”.
In Greek Chiro, to anoint, and in Hebrew mashah denoted a cultic consecration. Through consecration, a king, a priest, a prophet, an altar were specially set part. The anointing would confer the Spirit’s power, making him the anointed one, in Hebrew, the Messiah of the Lord.
The New testament applies to Jesus the Old testament texts concerning the anointing of the King-Priest. A priestly anointing was not narrated of Jesus, because he was the high priest, not like Aaron but according to the order of Melchizedek. While a prophetic anointing had been attributed to Jesus it was related to His baptism.
Jesus is the anointed Messiah.
We have all been anointed at Baptism and are called to be other Christ’s, Christians.