Where does “Δωδεκάνησα” come from?

Δωδεκάνησα (Greek) comes from Greek δώδεκα, from Ancient Greek δώδεκα, from Proto-Indo-European *dwoΗdeḱm̥.

Ancestry of “Δωδεκάνησα”, step by step

Step	Language	Word	Meaning
1	Greek	δώδεκα	twelve
2	Ancient Greek	δώδεκα	twelve
3	Proto-Indo-European	*dwoΗdeḱm̥	—

Δωδεκάνησα — Etymology, Origin & Word History | Etymology Explorer