Where does “orthodoxus” come from?

orthodoxus (Latin) comes from Ancient Greek ὀρθόδοξος, from Ancient Greek ὀρθός, from Proto-Hellenic ortʰwós, from Proto-Indo-European h₃r̥dʰwós, from Proto-Indo-European h₃erdʰ-, from Proto-Indo-European -wós — Creates adjectives from verb stems.

orthodoxus (Latin): orthodox