"defense, justification," 1784, the Latin form of apology (q.v.); popularized by J.H. Newman's "Apologia pro Vita Sua" (1864). It preserves the older sense of the English apology and the sense of the Greek original, especially as used by the Church fathers.
In common Greek, apologia refers to the speech that an accused person delivered in court, rejecting the charges filed against him or her. The apologists of the second century chose this term because they wanted to show that the charges filed against Christians were unjustified and that the truths of their faith could be described and defended. An apologia was dedicated to the Roman empoeror, who certainly never read it. [Max L. Stackhouse, "Apologia," 1988]