Where does “ether” come from?

ether (Old French) comes from Latin aethēr, from Ancient Greek Αἰθήρ, from Ancient Greek αἴθω, from Proto-Hellenic *áitʰō.

Ancestry of “ether”, step by step

Step	Language	Word	Meaning
1	Latin	aethēr	—
2	Ancient Greek	Αἰθήρ	Upper Air
3	Ancient Greek	αἴθω	To ignite, kindle, light; To burn, blaze
4	Proto-Hellenic	*áitʰō	—