From here:
Nobody's explicitly stated that Optimus, Prime, Ultra, Magnus, Maximus etc. are from Latin, or that other names are from other language sources. But we know it because it's common knowledge and pronunciation rules are similarly applied.
This would be true if Caminus had been absorbed into English in that form or a similar form. English pronounces words like Optimus, Prime, Ultra, Magnus and Maximus differently from Latin, but this is different because these words exist in English in these forms or similar forms. Caminus doesn't. The nearest English equivalent of caminus is "chimney" which we get from Old French cheminee, and even this pronunciation has mutated because the pronunciation of cheminee is something like "shommee-neh". In fact, RiD Optimus Prime's voice actor Neil Kaplan has a voice-character based on the original Latin pronunciation of Optimus which he calls "Optimoose."
You can't simply chalk down isolated mispronunciations as language evolution (by this logic George Dubya's mispronunciation of "nuclear" as "new-kewlar" and reference to the Greek people as "Grecians" would be correct), that's a wholly different thing. Also, as explained 2 posts ago, language evolution in languages was effectively halted after the advent of the printing press and languages like English have had relatively very little change in the past 600 years.
P.S.: if authors don't want people to notice hold standards of pronunciation for names, then just invent entirely fictitious ones. If you're going to draw references from the real world then of course people will naturally refer to them. It's like how Spider-Man 2 claimed that you can make nuclear fission from a single atom of tritium (H3O)... you literally cannot! On the other hand you can imbue fictitious metals like adamantium, vibranium or even transformium with magical properties because they're not real - there's no real world reference for anyone to disclaim it.