The plaque the Romans placed above Jesus's head as he writhed in pain—"King of the Jews"—was called a titulus and, despite common perception, was not meant to be sarcastic. Every criminal who hung on a cross received a plaque declaring the specific crime for which he was being executed. Jesus's crime, in the eyes of Rome, was striving for kingly rule (i.e., treason), the same crime for which nearly every other messianic aspirant of the time was killed.
Reza Aslan, Zealot: The Life and Times of Jesus of Nazareth
cross, inri, jesus