Where does “κυριακόν” come from?

κυριακόν (Koine Greek) comes from Ancient Greek Κύριος, from Proto-Hellenic *kúrios.

Ancestry of “κυριακόν”, step by step

Step	Language	Word	Meaning
1	Ancient Greek	Κύριος	Lord
2	Proto-Hellenic	*kúrios	—

κυριακόν — Etymology, Origin & Word History | Etymology Explorer