What is an Ichthus?

Ichthus (ΙΧΘΥΣ) is the Greek word for fish
 

This symbol was used primarily amongst Christians in early church history (1st and 2nd century A.D.) The symbol may have been adopted in Alexandria, Egypt, which at the time, was a heavily active seaport. It was the port in which many goods were brought over from the European continent. Because of this, it was first used by the peoples of the sea as a symbol of a familiar deity, in this case, Jesus Christ.

The symbol was later used as a means of identifying or acknowledging a fellow believer in Christ without the need for any verbal communication being exchanged.

During the reign of Emperor Nero (54 A.D.- 68 A.D.), and throughout the reign of the Roman Emperors, Christians were commonly persecuted, tortured, and put to death because of their Christian faith. In 64 A.D., great fire broke out in Rome, destroying portions of the city and economically devastating the Roman population. Nero himself was suspected as the arsonist by historian Suetonius, claiming he played the lyre and sang the 'Sack of Ilium' during the fires. To defer the blame, Nero targeted a relatively new religious sect: Christianity. He ordered Christians to be thrown to dogs, while others were crucified and burned.

Roman soldiers spread throughout the empire, were stationed to keep order and to act as police. Often, when a soldier spotted a suspected Christian, he would report it to his superiors, who in turn would order the Christian's arrest and interrogation. Often Christians would be harassed or even tortured in order for them to recant their beliefs and conform to the polytheistic Roman religion. Frequently, death would result in those that did not submit.

During this time of persecution, Christians would often draw an ichthus on the ground, or on the walls of caves or buildings, in an example of ancient hobo code, letting travelers know that they were in the presence of other followers. The ichthus indicted that the marked location was a safe to meet and talk about ones beliefs without fear of subjugation.