There is no agreement yet as to the etymology of the name "Sclavenes," first attested, almost simultaneously, in Procopius of Caesarea (in Greek) and Jordanes (in Latin). In Old Church Slavonic the word (Slaviane) is first attested in tenth-century texts produced in Bulgaria, but preserved only in much later manuscripts. If, as many linguists now believe, the name was initially a Slavic self-designation of some group on the sixth-century Danube frontier of the eastern Roman empire, then it was surely derived from a place-name, much like other ethnic names in Slavs with an "-ene" ending. Theories about the name deriving from Slavic words for "fame" or "word" are now largely discredited. Around 550, a shorter version of the name appeared in the works of Agathias of Myrina and John Malalas. Most likely coined in Constantinople, "Sklavos" was quickly reproduced in Latin as "Sclavus," the word from which "Slav" derives in most Romance and Germanic languages. In both Greek and Latin, "Slav" gradually replaced "Sclavene" after ca. 700. Almost at the same time, Sklavinia came into use, a word employed to refer to a territory inhabited by Sclavenes or under the authority of a Sclavene chieftain. Sklavinia is first attested in the History of Theophylact Simocatta, but the word was used especially by early ninth-century authors, such as Theophanes Confessor. It is also attested in Latin in contemporary Carolingian sources.
Jonas of Bobbio's Life of Saint Columbanus and the Chronicle of Fredegar are the first Latin sources to mention Sclavenes under a different name, Wends (Veneti, Venedi, or Winedi), later applied with some consistency to Slavic-speaking groups on the eastern frontier of the Frankish realm. Contemporary sources in Greek, such as the second book of the Miracles of Saint Demetrius used "Sclavenes" as an umbrella-term for a variety of tribal groups (Drugubites, Sagudates, Belegezites, Berzites, and Rynchines), some of which participated in attacks on the city of Thessalonica, while others remained on good terms with its inhabitants.Florin Curta