Bold and clichéd, profound and kitschy, the Christian fish symbol has achieved international celebrity one bumper at a time. Its detractors have ridiculed the message by adorning their own bumpers with walking Darwin fish and "No god but Allah" sharks. Yet for many Christians, the rudimentary design remains one of the faith's most enduring and treasured symbols, second only to the cross.

Watery wordplay

Long before the fish swam the streams of metropolitan traffic jams, Greek and Roman pagans used the design to symbolize feminine fertility and deity. They created the fish symbol by interweaving two crescent moons, which is the heavenly body often associated with goddesses.

The fish's spawning as a Christian symbol during the first century is similarly esoteric. Using the Greek word for fish, Ichthys, the compilers of a collection of religious teachings called the Sibylline Oracles created an acrostic: Iesous Christos theou huios soter, or "Jesus Christ Son of God Savior." This acrostic is now commonly embedded in modern fish symbols.

The fish gained increased prominence when early church leaders, with eyes and ears tuned to allegory, promoted other creative usages. Tertullian (c. 160-c. 225) taught that just as water sustains fish, "We, little fishes, after the image of our Ichthys, Jesus Christ, are born in the water." This aquatic birth is baptism, God's promise of new life and sustaining power.

Augustine of Hippo (354-430) believed the symbol suited Jesus well because "he was able to live … without sin in the abyss of this mortality as in the depth of waters."

Mark of the subversives

As persecution of Christians became more frequent and intense in the Roman Empire, the fish symbol became a password shared among underground believers. They used the fish to mark secret gathering places, especially within the catacombs. In this catacomb art the symbol was frequently coupled with communion imagery—the fish is depicted swimming with bread and a cup of wine on its back. The fish symbol also appeared on Christian gravestones and jewelry, and marked the homes of believers. After the threat of persecution had passed, the fish was inscribed on the Constantinian Church of the Nativity in Bethlehem.

Since the fish symbol was known among pagans, it remained a more discreet and thus effective identifier for the persecuted Christians than a cross. Secrecy often meant the difference between life and death for believers, or even the church's very survival. One story recounts how the fish symbol enabled fellow Christians to work together even when they didn't know each other. When meeting a stranger on the road, Christians would sometimes draw one arc of the fish in the dirt. If the stranger reciprocated by drawing the other arc, the believers could reveal their faith to each other without alerting Roman authorities and spies.

Go fish!

The symbol's widespread dissemination has been aided through the years by the many scriptural references to fish, not to mention their place as a nutritional staple. In Jesus' time, the Jews often celebrated important feasts by eating fish—a practice depicted in some artistic renderings of the Last Supper. And Jesus chose fish to multiply miraculously and feed to the multitudes.

Not only were fish frequently present at Jesus' dinner table, they also provided him with teaching illustrations. He apparently so amazed John that the apostle noted how, at Jesus' behest, Peter dragged ashore a bursting net filled with exactly 153 fish. And of course, when calling the fishermen Peter and Andrew to follow him, Jesus said they would become "fishers of men." Evangelistically motivated Christians of all ages have readily adopted this commission as their own.