Where does “εχθρός” come from?

εχθρός (Greek) comes from Ancient Greek ἐχθρός, from Proto-Indo-European h₁eǵʰs — out.

εχθρός (Greek): enemy

Definitions

Step	Language	Word	Meaning
1	Ancient Greek	ἐχθρός	hated, hateful; hating, hostile; enemy
2	Proto-Indo-European	h₁eǵʰs	out

εχθρός — Etymology, Origin & Word History | Etymology Explorer