1813, but in reference to the Wends; 1861 as "native of Serbia," from Serbian Srb, perhaps from a root meaning "man." Serbian is attested from 1848 as a noun, 1876 as an adjective. More common in 19c. was Servian.
seraglio
serape
seraph
seraphic
Serapis
Serb
Serbian
Serbo-
sere
Serena
serenade