What is the word for the thief in the every day language of your country and in the New Testament?

Ancient Greek made a distinction between thieves and robbers: kleptēs vs lēistēs or harpax. Both kleptēs and lēistēs are used in the New Testament; the men crucified with Jesus were lēistai.

The Modern Greek vernacular had lost the word lēistēs, and had kept the word kleptēs (as kleftis) to refer to both thieves and robbers.

Brigands are robbers are thieves. Brigands were also celebrated in folksong as indomitable rebels, and formed the backbone of the Greek War of Independence. So brigands, as Klephts, were much feted in the newly independent Greece:

Klephts (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 catch is that Klephts were really just brigands. As folk songs make clear, they would rob rich Christian and rich Muslim alike. They fought the good fight during the War of Independence—and after the War of Independence, they went back to robbing the citizens of the new Greek State. Which was more than a little embarrassing if the new Greek State is using them as part of its foundation story.

The Greek State had a means to deal with this embarrassment: the introduction of Puristic Greek, as a move back towards Classical Greek. The indomitable heroes of the revolution could go on being called klephts. The current scoundrels holding up Greek nationals in mountain passes may well have been the exact same people; but they were not going to be called the same heroic name. They were listis (lēistēs): the ancient and Biblical word was brought back, to castigate them. (Those folk songs featuring the brigands robbing Christians were judiciously ignored, too.)

As a result, Modern Greek now has a word for robber, listis, a word for thief, kleftis, and a cognitive dissonance about the fact that kleftis is also a heroic indomitable hero type.