Chi-Rho and IHS: a history of the monograms of Christ's name

A monogram fuses several letters into a single sign. In Christian culture two monograms have spread enormously: the Chi-Rho, formed by the first two Greek letters of the name Christos, and the trigram IHS, taken from the first letters of the name Jesus. Both arose from very concrete writing habits, linked to the work of scribes, and only later acquired symbolic meanings and new interpretations.

From scribal abbreviations

In early Christian manuscripts certain especially revered names were abbreviated and marked with a horizontal stroke above them: God, Lord, Jesus, Christ, Spirit. Scholars call these forms nomina sacra, “sacred names”. In biblical papyri from the late second and third centuries the staurogram also appears, a tau and a rho superimposed to draw a small cross with a loop, used within the word stauros, “cross”.

The sign formed by a superimposed chi and rho was already used before Christianity as an abbreviation for common Greek words, for instance in the margins of papyri to mark a useful passage, or on some coins. Its religious value was decisively established only at the beginning of the fourth century, when it became an emblem of imperial power.

The sign of Constantine

Lactantius, in his work On the Deaths of the Persecutors, relates that before the battle of the Milvian Bridge, in 312, Constantine was told in a dream to have the heavenly sign of God marked on his soldiers' shields. Eusebius of Caesarea, in the Life of Constantine written years later, reports instead a vision of a luminous cross in the sky and describes the labarum, the imperial standard topped by the monogram within a wreath.

The two accounts do not agree, and their reliability is debated by historians, but the effect is clear: during the fourth century the Chi-Rho appeared on coins, sarcophagi, mosaics, lamps and everyday objects. It was often flanked by the letters alpha and omega, recalling the passage of Revelation in which God calls himself the beginning and the end of all things.

IHS and its readings

The trigram IHS comes from Greek, as an abbreviation of Iesous using the letters iota, eta and sigma. When Greek ceased to be familiar in the West, the eta was read as a Latin H and explanations multiplied: Iesus Hominum Salvator, “Jesus Saviour of mankind”, or In Hoc Signo, an echo of the motto associated with Constantine. These are later interpretations, not the origin of the sign, but they contributed greatly to its success.

In the fifteenth century the Franciscan Bernardino of Siena made the monogram, surrounded by sun rays, the centre of his preaching on the name of Jesus. The tablets he showed to the faithful also prompted accusations of superstition and a trial before the papal curia, from which the preacher was acquitted. In the following century the Society of Jesus adopted IHS as its emblem, spreading it to churches all over the world.

The history of the monograms shows how an abbreviation born to save space could become an imperial standard, the emblem of a religious order and an object of popular devotion. Before a Chi-Rho carved on a late antique lamp or an IHS painted on a Baroque façade, one reads, in a few strokes, a long history of scribes, sovereigns and preachers.