Apostolic Father

The Apostolic Fathers were Christian theologians who lived in the 1st and 2nd centuries AD, who are believed to have personally known some of the Twelve Apostles, or to have been significantly influenced by them. Their writings, though popular in Early Christianity, were ultimately not included in the canon of the New Testament once it reached its final form. Many of the writings derive from the same time period and geographical location as other works of early Christian literature that did come to be part of the New Testament, and some of the writings found among the Apostolic Fathers' seem to have been just as highly regarded as some of the writings that became the New Testament.

The label Apostolic Fathers has been applied to these writers only since the 17th century, to indicate that they were thought of as representing the generation that had personal contact with the Twelve Apostles. The earliest known use of the term "Apostolic(al) Fathers" was by William Wake in 1693, when he was chaplain in ordinary to King William and Queen Mary of England. According to the Catholic Encyclopedia, the use of the term Apostolic Fathers can be traced the title of a 1672 work by Jean-Baptiste Cotelier, SS. Patrum qui temporibus apostolicis floruerunt opera ("Works of the holy fathers who flourished in the apostolic times"), which was abbreviated to Bibliotheca Patrum Apostolicorum (Library of the Apostolic Fathers) by L. J. Ittig in his 1699 edition of the same.

The history of the title for these writers was explained by Joseph Lightfoot, in his 1890 translation of the Apostolic Fathers' works:

...[T]he expression ['Apostolic Fathers'] itself does not occur, so far as I have observed, until comparatively recent times. Its origin, or at least its general currency, should probably be traces to the idea of gathering together the literary remains of those who flourished in the age immediately succeeding the Apostles, and who presumably therefore were their direct personal disciples. This idea first took shape in the edition of Cotelier during the last half of the seventeenth century (A.D. 1672). Indeed such a collection would have been an impossibility a few years earlier. The first half of that century saw in print for the first time the Epistles of Clement (A.D. 1633), and of Barnabas (A.D. 1645), to say nothing of the original Greek of Polycarp's Epistle (A.D. 1633) and the Ignatian Letters in their genuine form (A.D. 1644, 1646). The materials therefore would have been too scanty for such a project at any previous epoch. In his title page however Cotelier does not use the actual expression, though he approximates to it, SS. Patrum qui temporibus Apostolicis floruerunt opera; but the next editor [Thomas] Ittig (1699), adopts as his title Patres Apostolici, and thenceforward it becomes common.

...
Wikipedia