STRONGS NT 2312: θεολόγοςθεολόγος, θεολογου, ὁ (Θεός and λέγω), in Greek writings (from Aristotle on) one who speaks (treats) of the gods and divine things, versed in sacred science; (Grossmann, Quaestiones Philoneae, i., p. 8, shows that the word is used also by Philo, especially of Moses (cf. de praem. et poen. § 9)). This title is given to John in the inscription of the Apocalypse, according to the Rec. text, apparently as the publisher and interpreter of divine oracles, just as Lucian styles the same person θεολόγος in Alex. 19 that he calls προφήτης in c. 22. The common opinion is that John was called θεολόγος in the same sense in which the term was used of Gregory of Nazianzus, viz. because he taught the θεότης of the λόγος. But then the wonder is, why the copyists did not prefer to apply the epithet to him in the title of the Gospel.

From theos and didasko; divinely instructed -- taught of God.

see GREEK theos

see GREEK didasko