This answer to another question indicates that several of the showrunners of Star Trek had an interest in the Roman Empire, and that influenced their design and construction of the Romulan Empire. Terms like "consul," "romulan," "reman," and more are direct references to the Roman Republic and Empire.
But is there an in-universe explanation for the heavy use of terminology from Earth's history to refer to an alien race? Did some history nerd in Starfleet notice some similarities and decide to apply some historical terms to the newly discovered species? Or perhaps did the Romulans themselves, upon reviewing Federation history, choose their own "English" names to match an empire they identified with?
Or is this simply not discussed, in-universe?