Since the earliest times of Christianity, the title “Father” was already in use for the leaders of various religious communities. The bishops, who are the shepherds of the local church and the authentic teachers of the faith, were also given the title “Father” as direct successors to the apostles who became fathers themselves through the Gospel of Christ. In fact, St. Paul, in his letter to the Corithians, referred himself to be a father, as it reads: “For I became your father in Christ Jesus through the gospel” (1 Corinthians 4:15).
Furthermore, in a letter written by Dionysius, patriarch of Alexandria (A.D. 248-264), to Philemon, a Roman presbyter, it reads: “I received this rule and ordinance from our blessed father, Heraclas” (Eusebius, Historia Ecclesiastica Book VII, chapter 7.7). Thus, it is regarded that the usage of the term was very common for the leaders of the church not just in the time of Heraclas of Alexandria (A.D. 232-246) but even before that.
On the other hand, in an early form of his rule, St. Benedict (d. c. A.D. 547) designated the title “Abbot” to spiritual confessors, since they were the guardians of souls. Moreover, the word “abbot,” denoting the leader in faith of the monastic community, is derived from the word abba, the Aramaic Hebrew word for “father.”
Later, in the Middle Ages, the term “Father” was also widely known as being used to address the mendicant friars since by their preaching, teaching and charitable works they cared for the spiritual and physical needs of all of God’s children. In more modern times, the heads of male religious communities, or even those who participate in ecumenical councils such as the Second Vatican Council, are also given the title “Father.”
Despite these precedents, the use of “Father” as the formal title for all priests, whether attached to a diocese or members of a religious order, has become very customary in English-speaking countries as the Irish immigrants spread it to the United States in 1840’s. Also, when Henry Edward Cardinal Manning was archbishop of Westminster (1865-1892), he worked hard to establish this custom as the universal practice in England as well.
The term “Father” was derived from the Old English “fæder” meaning “he who begets a child”, which was originally from an Indo-European root shared by Latin pater and Greek patēr. Thus, like St. Paul, a priest is also a father because “for in Christ Jesus I have begotten you through the gospel” (cf. 1 Corinthians 4:15).