Klephts (/klɛfts/; Greek κλέφτης, kléftis, pl. κλέφτες, kléftes, which means “thief” and perhaps originally meant just “brigand”) were highwaymen turned self-appointed armatoloi, anti-Ottoman insurgents, and warlike mountain-folk who lived in the countryside when Greece was a part of the Ottoman Empire. They were the descendants of Greeks who retreated into the mountains during the 15th century in order to avoid Ottoman rule. They carried on a continuous war against Ottoman rule and remained active as brigands until the 19th century.
The terms kleptomania and kleptocracy are derived from the same Greek root, κλέπτειν (kléptein), “to steal”.
Source: Klepht – Wikipedia