Ptolemy mentions the “Serboi” a population that lived in the Caucasus. The name derives from “Serv” which in Latin means “guardian”, because the Serbs were animal guardians. This explains that the Serbs come from the Caucasus.

Transcribed:

“In his description of Sarmatia, Ptolemy also mentioned the “Serboi” who lived, along with some other tribes, between the northeastern foothills of the Caucasus and the Volga (Ptolemy, Geography V, 8, in Gimbutas 1971, 60). Moszyński derived the name from Indo-European *ser-, *serv-, that is, “guard, protect,” a cognate of Latin servus. Originally, it probably meant “guardians of animals,” in other words, “shepherds.” In Sarmatian, *serv-turned into *xarv-, very close to “Hrvat,” “Croat.” P. S. Sakać discovered Persian inscriptions of the time of Darius, mentioning a Persian province and its people close to modern Afghanistan, Harahvaiti, Harahvatis, Horo-hoati.”

Reference

The Role of Migration in the History of the Eurasian Steppe: Sedentary Civilization vs. ‘Barbarian’ and Nomad.