How does Greek work and under what circumstances is this sort of inversion of affixes/word components allowed?

There are two things that lead me to believe that the word was coined by a present-day Greek rather than some classical philologist on her lunch break: the transcription of the words and the inversion of the number morphemes.

First, Friday. The Classical Greeks didn't really have a Friday before they were christianized. So paraskeue: beging pronounced in the odern Greek manner, /paraskevi/. (Note that in words like euthanasia and euphemism, the eu- prefix is pronounced /ju/, not /ef/ like it would be, with the ypsilon becoming an f or v depending on environment.) Now, in Classical Greek, 13 is treis kai deka '3 and 10', but in Modern Greek it's dekatreis (not that the ei diphthong gets reduced to i, so /dekatris/). The order of the morphemes changed during the 2000 year development of Classical Greek to Koine to Modern Greek. I would spell treiskaidekaphobia with the ei intact, but others reduce it. Hope that helps.