The letters are frequently found on the top of crucifixes and are straight out of the Bible.
In the the first three Gospels of Matthew, Mark and Luke, it is narrated that after Jesus is nailed to the cross, the soldiers “placed over his head the written charge against him: This is Jesus, the King of the Jews” (Matthew 27:37).
The Gospel of John expands on this particular part of the Passion story of Jesus, explaining how the Jewish leaders protested against this sign. Pilate is the one who orders the sign and ensures that it is written in multiple languages for all to read.
Pilate also had an inscription written and put on the cross. It read, “Jesus the Nazorean, the King of the Jews.” Now many of the Jews read this inscription, because the place where Jesus was crucified was near the city; and it was written in Hebrew, Latin, and Greek. So the chief priests of the Jews said to Pilate, “Do not write ‘The King of the Jews,’ but that he said, ‘I am the King of the Jews.’” Pilate answered, “What I have written, I have written.” (John 19:19-22)
The inscription Pilate had written is depicted on crucifixes with the abbreviation INRI.
This refers to the Latin translation of Pilate’s charge, Iesus Nazarenus, Rex Iudaeorum (Jesus the Nazarene, King of the Jews). On occasion the first letter is rendered as a “J” instead of an “I,” but the Latin is still the same.
Since the Catholic Church was initially located in the Roman Empire and Latin became the “official” language of the Roman Church, INRI was favored over the Greek or Hebrew words for the inscription.
The abbreviation reminds us that Pilate’s charge, while meant to be mocking, is true: Jesus truly is our king, who came to save us from sin and death. His throne was the cross and he rules over us in love and mercy. Jesus is the one true king that we call all rally behind.