Where does “Ἀντικύθηρα” come from?

Ἀντικύθηρα (Ancient Greek) comes from Ancient Greek ἀντι-, from Ancient Greek ᾰ̓ντῐ́ — opposite.

Ancestry of “Ἀντικύθηρα”, step by step

Step	Language	Word	Meaning
1	Ancient Greek	ἀντι-	anti-, against; like, reminiscent of
2	Ancient Greek	ᾰ̓ντῐ́	opposite

Ἀντικύθηρα — Etymology, Origin & Word History | Etymology Explorer