The letters “INRI” are initials for the Latin title that Pontius Pilate had written over the head of Jesus Christ on the cross (John 19:19). Latin was the official language of the Roman Empire.
The words were "Iesvs Nazarenvs Rex Ivdaeorvm." Latin uses “I” instead of the English “J”, and “V” instead of “U” (i.e., Jesus Nazarenus Rex Judaeorum). The English translation is "Jesus of Nazareth, the King of the Jews."
The Early Church adopted the first letters of each word of this inscription “INRI” as a symbol. Throughout the centuries INRI has appeared in many paintings of the crucifixion.
By the way, Pilate's title for Christ was actually written in three languages.
And Pilate wrote a title, and put it on the cross. And the writing was, JESUS OF NAZARETH THE KING OF THE JEWS. This title then read many of the Jews: for the place where Jesus was crucified was nigh to the city: and it was written in Hebrew, and Greek, and Latin. Then said the chief priests of the Jews to Pilate, "Write not, 'The King of the Jews;' but that he said, 'I am King of the Jews'." Pilate answered, "What I have written I have written."
-John 19:19-22 (KJV)
The initials of the Latin sentence which was placed upon the cross: Jesus Nazarenus Rex Judaeorum, meaning Jesus of Nazareth, King of the Jews. The Rosicrucians used them as the initials of one of their Hermetic secrets: Igne Natura Rerun vatur Integras meaning that by fire, nature is perfectly renewed. They also adopted them to express the names of their three elementary principles salt, sulphur, and mercury by making them the initials of the sentence, Igne Nitrum Roris Invenitur. Ragon finds in the equivalent Hebrew letters nor the initials of the Hebrew names of the ancient elements: Iaminim, water; Nour, fire; Ruach, air; and Iebschah, earth.
I- IGNI - TUBIG
N- NATURA - APOY
R- RENOVATOR - HANGIN
I- INTEGRA - LUPA
