Where does “κλέφτης” come from?

κλέφτης (Greek) comes from Byzantine Greek κλέφτης, from Ancient Greek κλέπτης, from Ancient Greek κλέπτω, from Proto-Hellenic klépťō, from Proto-Indo-European klép-ye-ti, from Proto-Indo-European ḱlep-, from Proto-Indo-European klep- — to steal.

κλέφτης (Greek): thief, stealer; klepht