The name "Serb" is ancient. It is non-Slavic in origin and more likely than not original Serbs were overlords of the Slavs. Tha name 'Serb' designates not only the population in the Balkan peninsula but of Lusatia as well. Lusatia, a region in Eastern Germany is inhabited by a nation the Germans call the Wends from which the Greeks derived the word Venedi. The name "Serb" is ibero-caucasian in origin. In comes from the word "Ser" meaning "man", with the "bi" added to make the plural form. The Serbs were part of the Caucasian Race much like the Georgians, Mingrelians, Lezghians, Ingush, and spoke a language simmilar to these peoples. At some point in the history of the Serbs, this Old Serb language stood side by side with the Slavic language in White Serbia (Porphyrogenitus) and likely even in the first 300 years leading up to the formation of the Serb state on the Balkans in the 9th century. Even to this day, the Serb language has at least a third as many words in its vocabulary than other Slavic languages. This is because of the influence of Old Serb and Illyrian as well as Turkish on the Slavic language spoken by Serbs today.
here is an examples of the Old Serb words which exist side by side with Slavic words in the modern Serb language.
A word of Slavic origin in modern Serbian:HLEB
A word of Old Serb origin in modern Serbian:PITA
English translation:a bread – a loaf