I'm somewhat of a comparative/historical linguistics beginner here -- apologies if I don't know the correct formal terminology.
So I understand (from looking at Beekes) that ἀΐδιος derives from the adverb αἰεί (itself from *aiwes-i).
Understanding the origins of -ι(ος) here is simple enough; yet I'm not quite sure where -δ- comes into play. The only really relevant comment I've found is "Usually Indo-Europeanists do not claim to discern a common meaning or function behind any individual root determinative such as *-d (Persson 1912:556)."
Am I reading about something different here, or is this where we're to find the origins of -δ- in things like ἀΐδιος?
When I've looked at some other Greek adjectives derived from adverbs, they not only have -διος but -ίδιος, like μαψίδιος from μάψ. So is it actually the case that ἀΐδιος "contains" the suffix -ίδ(ιος) (perhaps with other vowels dropping out because of "redundancy")?
Finally, is -ίδιος the same as the normal ίδιος, in terms of denoting similarity / being reflexive? (And how exactly are we to understand/define its presence in an adjective -- something like having a sense of "pertaining to..."?)
Thanks in advance!
Stewart Felker,
University of Memphis