Where does “ἑταῖρα” come from?

ἑταῖρα (Ancient Greek) comes from Ancient Greek ἑταῖρος, from Proto-Indo-European swé — self.

Ancestry of “ἑταῖρα”, step by step

Step	Language	Word	Meaning
1	Ancient Greek	ἑταῖρος	comrade, companion, partner, friend; pupil,...
2	Proto-Indo-European	swé	self

ἑταῖρα — Etymology, Origin & Word History | Etymology Explorer