Where does “καθοίκι” come from?

καθοίκι (Byzantine Greek) comes from Ancient Greek καθ' — Apocopic form of κατά.

Ancestry of “καθοίκι”, step by step

Step	Language	Word	Meaning
1	Ancient Greek	καθ'	Apocopic form of κατά

καθοίκι — Etymology, Origin & Word History | Etymology Explorer