The Christos Hat

Chi-Rho (XP) are the first two letters in the Greek word for Christos, which when superimposed is often called the Chi-Rho Cross. This symbol has been used since the early days of Christianity when Christians would be persecuted for their believes. And later would be used in Christian art throughout the Roman Empire. Fun fact, this symbol has been seen all over the catacombs and other ancient places. 

The Alpha and Omega are the first and last letters of the Greek Alphabet, which represents the beginning and the end. In the book of Revelation 1:8, Christ says, "I am the Alpha and the Omega,” says the Lord God, “who is, and who was, and who is to come, the Almighty."

These 2 letters symbolize that Christ is the beginning and the end of all creation.