The Greek word for fish is "ixthus" or "icthus." Five Greek letters form the word “ixthus,” and those letters inside the fish form an acrostic which is a message that Christians clearly identified with. The first letter represented the word Jesus. The second letter represented the word Christ, the next two, God Son, and the final letter represented the word Savior. This adds up to “Jesus Christ is God’s Son, the Savior.”
During the early days of Christianity, Christians were often put to death for practicing their faith, so they worshiped in secret places. A fish painted on the outside door of a house let other Christians know that they would be safe and welcome inside. The Christian fish symbol is now often used to identify Christians and/or Christian businesses.
Fulfilled ProphecyJesus knew he was going to be killed and he knew about the hardships the early Christian Church would endure, he stated it many times long before as recorded in the Gospels