How to know if another person is also a Christian under persecution if not using some symbol? The fish symbol of Christianity was a recognizable sign.
Christianity is still the most persecuted religion in the world. Since Christ himself was crucified, it is not difficult to imagine that the beginnings of Christianity were not easy either. And they really weren’t: in the first three centuries, the persecution of Christians was frequent and brutal. Many converts had to express their faith in Christ secretly and illegally.
How Could a Christian Know if Another Person Was Also a Christian in These Cruel Conditions?
In addition to being cautious and informing themselves about others in advance as much as possible, they also used secret codes that could be used to determine that a person of the same religion was in front of them.
One of these ciphers was the word ‘Ichthys’ or ‘Ichthus’ – a word meaning ‘fish’ in ancient Greek (ἰχθύς).
It was a serious assumption that when an illegal Christian found himself in front of someone he thought was also an illegal Christian; he drew a curve or a crescent on the ground. If another person drew a second crescent next to that curve in such a way that the two curves formed a fish, it was very likely that that person was following Jesus and knew the Christian “secret code.”
But why fish? Because the letters that make up the Greek word “fish,” when written in capitals, as Ι Χ Θ Υ Σ, form an acronym from the initial letters of the term Iēsous Christos Theou Yios Sōtēr, which means: Jesus Christ the Son of God the Savior (ancient Greek: Ἰησοῦς Χριστός Θεοῦ ͑Υιός Σωτήρ).
In this way, besides the image of the Good Shepherd and the cross, the fish became one of the first symbols of Christianity.
“Ichthys” was also used in Christian catacombs during the persecution of the community. With the help of this sign, Christians knew where the graves of their brothers in faith were.