That ethnonym is attested by Procopius in Byzantine Greek as Σκλάβοι (Skláboi), Σκλαβηνοί (Sklabēnoí), Σκλαυηνοί (Sklauēnoí), Σθλαβηνοί (Sthlabēnoí), or Σκλαβῖνοι (Sklabînoi),[10] while his contemporary Jordanes refers to the Sclaveni in Latin.
[13] In the source dating to 898 included in the Primary Chronicle, the term is used both for East Slavic tribes and more often for a people (in the Kievan Rus' society, alongside Varangians, Chuds and Kriviches).
[27] S. B. Bernstein speculated that it derives from a reconstructed Proto-Indo-European *(s)lawos, cognate to Ancient Greek λαός (laós) "population, people", which itself has no commonly accepted etymology.
[28] According to the widespread view known since 18th century, the English word slave, which arrived in modern language from Middle English sclave, from Old French esclave, from Late Middle High German sklave, from Medieval Latin sclāvus, from Late Latin Sclāvus, from Byzantine Greek Σκλάβος [Sklábos], Έσκλαβήνος [Ésklabḗnos] and displaced native Old English þēow, derives from Byzantine loanword from a Slavic gen self-name *Slověninŭ - Σκλάβινοι [Sklábinoi], Έσκλαβηνοί [Ésklabēnoí], that came to mean 'prisoner of war Slave', 'slave' (Σκλάβος, Έσκλαβήνος, Late Latin Sclāvus) in the 8th/9th century, because they often became captured and enslaved (see also Saqaliba).
[38][39] An alternative contemporary hypothesis states that Medieval Latin sclāvus via secondary form *scylāvus derives from Byzantine σκυλάω [skūláō, skyláō], σκυλεύω [skūleúō, skyleúō] - "to strip the enemy (killed in a battle)", "to make booty / extract spoils of war".