- These letters belong under this head only in appearance as they are in reality the first two letters of the Greek word Christos, meaning "Christ." The X is the Greek letter Chi and is equivalent to the English letters "ch"; the P is called Rho and is the same as the letter "r;" they thus represent the first three letters of the word Christ. These two Greek letters are used in Church decorations either separately or as a monogram, as a symbol or emblem of our Lord.
American Church Dictionary and Cyclopedia. — New York, Thomas Whittaker. William James Miller, M.A., B.D.. 1901.