The Epistle of Diognetus is one of the first Christian apologetic writings. The text is dated to be around the mid-100s AD. The word 'apology' in modern use has deviated from its original definition. In ancient Greek (and subsequently ancient Latin), an apologia was a reasoned argument in defense of something. It is thought that Diognetus was the intended recipient, however, the name for the author - 'Mathetes,' is translated as 'student.' It's likely that this was not the author's name but a self-described title.