Logic is the beginning of wisdom, Valeris, not the end...
Chronologically, ENT "Borderland" is our first mention of Orions, and unsurprisingly the mention is made by T'Pol, with the human heroes just meekly listening and learning. Might be it's a Vulcan name for the culture. Might be it's an Orion name directly adopted by Vulcans. Might be the Universal Translator fouls up whatever T'Pol is saying, and Orion in fact is a fundamentally human name for the bunch.
Timo Saloniemi
So, maybe they are really Ohryans and the UT just mistranslated it.