In Acts Luke mentions Jason being hauled before the city officials
But the Jews were jealous, and taking some wicked men of the rabble, they formed a mob, set the city in an uproar, and attacked the house of Jason, seeking to bring them out to the crowd. And when they could not find them, they dragged Jason and some of the brothers before the city authorities, shouting, "These men who have turned the world upside down have come here also, and Jason has received them, and they are all acting against the decrees of Caesar, saying that there is another king, Jesus." And the people and the city authorities were disturbed when they heard these things. And when they had taken money as security from Jason and the rest, they let them go. (Acts 17:5-9)The word translated city authorities is politarches (πολιτάρχη). It occurs here twice but nowhere else in extant Greek literature (though apparently a similar term poli(t)archos may be known from classical Greek?). This led earlier critics to claim Luke was in error.
The word is a compound word constructed from polis (city) and arche (ruler). Even if this was a Lukan neologism it is hardly an error. Even so, an archaeological discovery in the 19th century revealed that politarches was an official title: a stone inscription on the Vardar Gate/ Arch in Thessolonica. This arch was near the Vardar River and spanned the famed Egnatian Way. It reads
∙ΠΟΛΕΙΤΑΡΧΟΥΝΤΩΝ ∙ΣΩΣΙΠΑΤΡΟΥ ·ΤΟΥ ·ΚΛΕΟΠΑΤΡΑΣ ·ΚΑΙ ∙ΛΟΥΚΙΟΥ ·ΠΟΝΤΙΟΥ ·ΣΕΚΟΥΝΔΟΥ ·ΥΙΟΥ ·ΑΥΛΟΥ ∙ΑΟΥΙΟΥ ·ΣΑ ∙ΒΕΙΝΟΥ ·ΔΗΜΗΤΡΙΟΥ ·ΤΟΥ ·ΦΑΥΣΤΟΥ ·ΔΗΜΗΤΡΙΟΥ ·ΤΟΥ ·ΝΕΙΚ ∙ΟΠΟΛΕΩΣ ·ΖΩΙΛΟΥ ·ΤΟΥ ·ΠΑΡΜΕΝΙΩΝΟΣ ·ΤΟΥ ·ΚΑΙ ·ΜΕΝΙΣΚΟΥ ∙ΓΑΙΟΥ ·ΑΓΙΛΛΗΙΟΥ ·ΠΟΤΕΙΤΟΥ ·ΤΑΜΙΟΥ ·ΤΗΣ ·ΠΟΛΕΩΣ ·ΤΑΥΡΟ ∙Υ ·ΤΟΥ ·ΑΜΜΙΑΣ ·ΤΟΥ ·ΚΑΙ ·ΡΗΓΛΟΥ ·ΓΥΜΝΑΣΙΑΡΧΟΥΝΤΟΣ ·ΤΑΥ ∙ΡΟΥ ·ΤΟΥ ·ΤΑΥΡΟΥ ·ΤΟΥ ·ΚΑΙ ·ΡΗΓΛΟΥ
The first word poleitarchountōn is a variant of politarches showing that this is not a Lukan neologism and that Luke was using an official term, much as he does elsewhere in his books. Other inscriptions containing this word have subsequently been found.
I have minimal concern about authors using neologisms and do not consider them errant. Nevertheless it is important to note that critics of Luke made something of this and they were shown to be incorrect while Luke was vindicated. Though this example may not currently be used against Luke, the fact that historical critics of Luke were proven wrong needs to be remembered when dealing with modern critics of Luke.
Further reading here, here, and here.