Where does “δούκα” come from?

δούκα (Greek) comes from Greek δούκας, from Ancient Greek δούξ, from Latin dux, from Latin dūcō, from Proto-Italic doukō, from Proto-Indo-European déwketi, from Proto-Indo-European dewk- — to pull, to draw; to lead.

δούκα (Greek): Genitive singular form of δούκας;...