And about the origin of South Slavs read this material of a Serbian author:
......imena "Srbin", serv, pretvorio su iranskome u charv, što je skupa sa sufiksom at dalo Choroatos i Hrvat. Bjelodano je jasno da su Srbi i Hrvati imali sličnu povezanost povijesti od najstarijih vremena
tolomej, koji je pisao u drugom stoljeću naše ere, također spominje Serboi među sarmatskim plemenima sjeverno od Kavkaza. Većina naučnika vjeruje da su i Srbi i Hrvati bili slavenska plemena s iranoskom vladajućcom kastom, ili da su prvobitno bili iranska plemena koja su stekla slavenske podanike. Negdje na početku sedmog stoljeća oba su plemena onsovala svoju kraljevinu u Srednjoj Evropi, Bijelu Hrvatsku koja je obuhvatala dio današnje južne Poljske, i Bijelu Srbiju, u današnjoj Českoj. Odatle su se i jedni i drugi doselili na zapad Balkana.
Now i will try with Google Translate maybe some serbian member can help with fixing the translation:
names ...... "Serb", serv, turned to the Iranian Charvi, which together with the suffix given at Choroatos and Croatia. Manifestly clear that the Serbs and the Croats had a similar relationship history from the earliest times:
Ptolemy, who wrote in the second century BC,
also mentioned Serboi among Sarmatian tribes north of the Caucasus. Most scientists believe that the Serbs and Croats were Slavic tribes with Iranian ruling caste, or
that were originally Iranian tribes who acquired Slavic subjects. Somewhere at the beginning of the seventh century, both tribes onsovala his kingdom in Central Europe, White Croatia which included part of present-day southern Polish, and White Serbia, in what is now the Czech Republic. From there they both are moved to the West Balkans.