The translation Christos is employed in the LXX for the Hebrew Messiah, meaning ‘anointed’; originally it applied to the king, who was anointed, as David by Samuel (1 Sam. 16: 13), and his successors (Ps. 2: 2; Dan. 9: 25), and in the NT to Jesus as the one who fulfilled the OT expectations (Luke 2: 11).
‘Christ’ was so often applied to Jesus, as the Messiah, that it virtually became a surname attached to Jesus (John 1: 17). Those who came to believe that the life, death, and resurrection of Christ was their guarantee of salvation were baptized into the Church, whose single reason for existing was its relation to Christ, and which shared his sense of urgency and expectation.