Question: "What does INRI stand for? What was written on the sign nailed to the cross above Jesus" head?"
Answer: John 19:19 records, "Pilate had a notice prepared and fastened to the cross. It read: JESUS OF NAZARETH, THE KING OF THE JEWS." John 19:20 continues, "Many of the Jews read this sign, for the place where Jesus was crucified was near the city, and the sign was written in Aramaic, Latin and Greek." Today, many times when the cross of Jesus is displayed, the letters INRI are placed on the sign above the cross. In Latin, the text "JESUS OF NAZARETH, THE KING OF THE JEWS" would have been written, "Iesus Nazarenus Rex Iudaeorum." Abbreviated, this phrase results in "INRI." It is unlikely that the letters INRI were truly on the sign that Pilate placed over Jesus' head, as John 19:20 specifically states that the sign was written in Aramaic, Greek, and Latin.
Although John's gospel refers to the writing as a "title," Mark and Matthew both refer to it as an "accusation." It was customary to set up over the heads of persons crucified the crime for which they suffered, and the name of the sufferer. The accusation on which Jesus had been condemned by Pilate was his claiming to be the King of the Jews. Ironically, the "crime" for which Jesus was crucified is not a crime at all, but an absolutely true statement. Not only is Jesus King of the Jews, He is the King of all " the King of kings and the Lord of lords (Revelation 17:14 and 19:16). He is King over all the universe and all its inhabitants. And it was not any crime of His own that was nailed to the cross; it was the crimes (sins) of everyone who would ever put his or her faith in Him for salvation. He has "blotted out the handwriting of ordinances that was against us, which was contrary to us, and has taken it out of the way, nailing it to the cross" (Colossians 2:14).
Just as the title King of the Jews was written in three languages, so do those of all nations and languages recognize Him as Savior, as indeed He is of all the elect of God whom He saves from all their sins, by bearing them in His own body on the cross, and of whom He is the able and willing, the perfect and complete, the only and everlasting Savior.