Theory about Iranian origin of the Serb ethnonym assumes that ancient Serbi / Serboi from north Caucasus (Asiatic Sarmatia) were a Sarmatian (Alanian) tribe.[21] The theory subsequently assumes that Alanian Serbi were subdued by the Huns in the 4th century and that they, as part of the Hunnic army, migrated to the western edge of the Hunnic Empire (in the area of Central Europe near the river Elbe, later designated as White Serbia in what is now Saxony (eastern Germany) and western Poland). After the Hunnic leader Attila died (in 453), Alanian Serbi presumably became independent and ruled in the east of the river Saale (in modern-day Germany) over the local Slavic population.[21][22] Over time, they, it is argued, intermarried with the local Slavic population of the region,[21][22] adopted Slavic language, and transferred their name to the Slavs.[23] According to Tadeuš Sulimirski, similar event could occur in the Balkans or Serbs who settled in the Balkans were Slavs who came from the north and who were ruled by already slavicized Alans.[22]
https://en.wikipedia.org/wiki/Origin...s_of_the_Serbs
https://upload.wikimedia.org/wikiped...avant_1000.png