Christograms
Over the centuries, monograms of the name of Jesus Christ have been used as Christian symbols. The IX monogram consists of the initial Greek letters of the name "Jesus Christ," "I" for Ιησούς, (Jesus in Greek) and "X" for Χριστος (Christ in Greek). The "IHS" Christogram, denoting the first three letters of the Greek name of Jesus, is usually written as a cypher, but sometimes as a monogram. Perhaps the most significant Christogram is the Chi Rho, formed from the first two letters of Χριστος.
Read more about this topic: Monogram