Where does “Dodecanese” come from?

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

Ancestry of “Dodecanese”, step by step

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