Turns out, it was the Greeks. Χριστος is how you write “Christ” in Greek and writers (including people who transcribed the Bible) have been using “X” as a convenient abbreviation of that since at least the 3rd and 4th centuries.
Turns out, it was the Greeks. Χριστος is how you write “Christ” in Greek and writers (including people who transcribed the Bible) have been using “X” as a convenient abbreviation of that since at least the 3rd and 4th centuries.