Beloved brothers and sisters in Christ,
Christ is in our midst! He was, is, and ever shall be.
According to tradition, it was Christ, of course, who re-named both His Disciples and various other in the New Testament (St. Mary Magdalene, for example). (See "Orthodox Tradition," Vol. XV, No. 4, pp. 26-27) "Scripture and Tradition"). Christians were also exhorted to take the name of Prophets and Saints by the authors of the first Catechetical texts of the primitive Church. It was also at this time that Liturgies were universally celebrated in honor of the Martyrs, Apostles, and Saints, when those having their names would commemorate them.
According to tradition, then, the commemoration of the names of holy persons, including the Mother of God, is Apostolic (hence the origins of the Service of the Elevation of the Panaghia). It grew out of the veneration of Martyrs and Saints.
With regard to the "Apostolic" origins of taking Christian names, let us cite one instance form the Apostolic Age that is well known in the Orthodox Church. According to Tradition, the Prince who martyred the Apostle Matthew, a certain Fulvian, afterwards became a Christian. When he was about to receive Baptism, a voice from on high declared to the Bishop who was about the Baptize him, "Do not call him Fulvian, but Matthew." He was thus named after the Apostle. (Saint Dmitri Rostov includes this story in his Collection of the Lives of the Saints, published in Moscow in 1914. It is also contained in older collections of the Lives of the Saints of the Orthodox Church, from which St. Dmitry derived many of the biographies in his collection.)
The traditional Catechetical texts on Baptism date to the first four centuries of Christianity and are called collectively, in Greek "Katechetikai Diatrivai." There are literally scores of works, both by Eastern and Western Fathers, that address the Baptismal and Mysteriological traditions of the Church. Let us simply quote an excellent work by Metropolitan Augustinos Kantiotes of Florina, Greece, Eis ten Theian Leitourgian, Praktikai Homiliai (Athens, 1977), in which he summarizes one aspect of the catechetical instructions in the Early Church:
"...In the ancient Church, the Church of the first centuries of Christianity...when the catechumens had been taught all that they were to learn, their instructors would take them back to the Bishop, and the Bishop would recommend that they change their pagan (secular) name and adopt Christian ones; these names were to remind them of holy personages of virtues (e.g. Agapios, from agape, "love"...)".
As for pre-fifth-century references to the taking of "Christian names," if we may use this obviously imprecise term, let us cite just a few from many, many such instances, in order to point out that our observations have not been simply casual:
St. Ev (u) stathios, whose pagan name was Placidas, was given the name "Evstathios" in Holy Baptism. He was martyred in 100 A.D. and his Baptism took place sometime in the 80s. His wife (Theopiste) was also given a Christian name, as were their two sons (Agapios and Theopistos). This life was compiled in the 11th century by Saint Symeon Metaphrastes.
In Eusebius' early 4th century Ekklesiastike Historia (Church History), we find references to the Christian practice of giving the names of the Apostles to children (Book VII, Chap. 25). Also in the same work, we read that the Egyptian Christians forsook their pagan names for Scriptural names--usually the names of Prophets (Book VIII, "The Martyrs of Palestine").
In his "Homilia Enkomiastike eis ton en Hagiois Patera hemon Meletion…" Saint John Chrysostom tells us that many Christians named their children after this great Saint (Patrologia Graeca, Vol. L).
Saint Prokopios of Gaza, writing in the early 6th century and speaking of the early (pre-Constantinian) Christian Martyrs, states that many of them took the names of "holy men" (Saints) for themselves. "With these names, they eagerly delivered themselves to martyrdom," he writes. This may seem inapplicable to the question at hand, but martyrdom in the Orthodox Church, at least, is considered "Baptism by blood." It is not unusual, then, that the Martyrs chose to take the names of Saints (Patrologia Graeca, Vol. L XXXVII, Part II, Epitome ton eis ton Propheten Isaian Exegeseon).
With regard to the celebration of the onomasterion (onomastike heorte or celebration of name or feast day), here again we must turn to the double witness of history and Holy Tradition. It is clear that Christians celebrated the Divine Liturgy in Apostolic times in memory of the Martyrs and Saints. Saint Polycarp, for example, was martyred on February 23, 155/6. The Christians in Smyrna issued a letter, To Martyrion toy Polykarpou, (The Martyrdom of Polycarp), in which they exhorted other Christians to celebrate the day of his Martyrdom and expressed their desire that the Lord "will permit us" (future tense) to gather in joy to continue such a celebration. That this practice of calling on the memories of the Saints in liturgical rites is, again, a complex one, we do not argue. Holy Tradition has always associated it with the earliest Christian Liturgies. And certainly there is clear evidence by the 2nd century of such a tradition. Holy Tradition also establishes that these celebrations were honored by those who bore the names of the Martyrs and Saints who were being commemorated. (Source: Orthodox Christian Information Center)
The Orthodox Christian tradition is to give only one name to the one who is baptized. The newly baptized person will consider that Saint whose name he bears as his/her patron and protector Saint. It our Orthodox Christian practice to honor our patron Saint on his/her feast-day, attend the Divine Liturgy, and receiving Holy Communion on that day. Also to turn to our Saint at times of distress, danger, illness, seeking his/her intercessions, protection, and guidance.
With agape in Our Savior,