"After eight days had passed, it was time to circumcise the child; and he was called Jesus, the name given by the angel before he was conceived in the womb" (Lk 2:21 ). As part of the Christmas celebration of the mystery of God-become-human, on January 3rd the Church reflects on the Holy Name of Jesus. Throughout Christian history, the name Jesus - meaning "God saves" - was invoked by Christians in prayer to verbalize all they had experienced through Jesus, their saving Lord: "Therefore God gave him the name that is above every name, so that at the name of Jesus every knee should bend. . . and every tongue confess that Jesus Christ is Lord, to the glory of God the Father" (Phil 2:9-11).
Already in the sixth century, the meditative "Jesus prayer" developed in the Eastern Churches as a way of dwelling in the reality of Jesus's saving mercy. In the Western Church, devotion to the Holy Name spread in the Middle Ages as part of the the growing emphasis on the humanity of Christ. In a particular way, this devotion was spread by the Franciscans, especially Bernardine of Siena, who in the 1400s carried about on his preaching tours a board with an icon of the Holy Name as a sign of penance and conversion.
For a very good discussion of Bernardine - including artistic depictions -- and the spread of devotion to the Holy Name, see: http://idlespeculations-terryprest.blogspot.com/2011/01/ihs-holy-name-of-jesus.html
As the Catechism of the Catholic Church summarizes: "the one name that contains everything is the one that the Son of God received in his incarnation: JESUS. The divine name may not be spoken by human lips, but by assuming our humanity, The Word of God hands it over to us and we can invoke it: "Jesus," "YHWH saves." The name "Jesus" contains all: God and humanity and the whole economy of creation and salvation. To pray "Jesus" is to invoke him and to call him within us. His name is the only one that contains the presence it signifies. Jesus is the Risen One, and whoever invokes the name of Jesus is welcoming the Son of God who loved me and who gave himself up for me" (#2666).
Dominic V. Monti, OFM, is a Franciscan Friar of Holy Name Province (USA) and currently professor of Franciscan Research in the Franciscan Institute of St. Bonaventure University. He devoted the greater part of his ministry to teaching the History of Christianity, in particular the history of the Franciscan movement. He has contributed two volumes to the Works of St. Bonaventure series and is author of Francis & His Brothers, a popular history of the Friars Minor.