Where does “ἀέριος” come from?

ἀέριος (Ancient Greek) comes from Ancient Greek -ῐος, from Proto-Indo-European -yós — Creates adjectives from noun or verb stems.

ἀέριος (Ancient Greek): high in the air

Definitions

Step	Language	Word	Meaning
1	Ancient Greek	-ῐος	belonging to; of”, “belonging to”, “pertaining to
2	Proto-Indo-European	-yós	Creates adjectives from noun or verb stems

ἀέριος — Etymology, Origin & Word History | Etymology Explorer