The Greek work for Christ is (transliterated) Xristos. As said, the "X" is the Greek "Chi," pronounced with a bit of a gutteral sound. Xristos/Christ in Greek means "The Annointed One." The Hebrew counterpart is "Messiach," which comes to us as Messiah. In the NT, both are used.
The "X" was used also in early Christian days to indicate Christians.
GM