In Hellenistic Greek, the word Ichthus (aka Ichthys or Ikhthus) means fish. It is composed of two intersecting arcs. One end of both arcs extends beyond the meeting point, creating the profile of a fish. The fish is a very significant symbol for Christians. Literally, the word Ikhthus means Jesus (I) Christ (KH), God’s (TH) son (U), Savior (S). More informally, it is known as the “sign of the fish”. Jesus Christ and His apostles were known as “fishers of men”
The symbol is believed to have been used in earlier times as a secret symbol by which Christians knew they were in the company of a friend. For hundreds of years after Christ, it was dangerous to be a Christian because the pagan Roman Emperors persecuted them. When meeting a person for the first time, one would scratch half the image on a wall, a rock or on dirt and if the other person understood what it is, he/she would complete the symbol.