Why X in oddXian?

The idea of X as an abbreviation for the name of Christ came into use in our culture with no intent to show any disrespect for Jesus. The church has used the symbol of the fish historically because it is an acronym. 

Fish in Greek (ichthus) involved the use of the first letters for the Greek phrase “Jesus Christ, Son of God, Savior.” So the early Christians would take the first letter of those words and put those letters together to spell the Greek word for fish. 

That’s how the symbol of the fish became the universal symbol of Christendom. There’s a long and sacred history of the use of X to symbolize the name of Christ, and from its origin, it has meant no disrespect. 

- RC Sproul