Middle English sclave, from Medieval Latin sclavus or Sclavus, from Byzantine Greek Σκλάβος (Sklábos), from earlier Σκλαβῆνος (Slabēnos), plural Σκλαβῆνοι (Slabēnoi), from Proto-Slavic *slověnji, *slověne (“those who speak meaningfully”), singular *slověninъ. Compare Old Church Slavonic словѣни (slověni), словѣнє (slověne, “Thessalonian Slavs”), Old East Slavic словѣне (slověne, “Slavs near Novgorod”).
Commonly thought to derive from Proto-Slavic *slovo (“word”), thus meaning "those who speak meaningfully" and contrasting with *němьcь (“foreigner”, literally "dumb/mute person"). However, that word is an s-stem and thus the inflectional stem of that word is *sloves-, so it cannot be the direct origin as it would lead to an expected form *slovesěni (compare Russian словесность (slovesnost')). Thus the most likely origin is the verb *sluti (“to be known”). Both words ultimately derive from Proto-Indo-European *ḱlew- (“fame”).
Slav (plural Slavs)
- A member of a group of peoples in Eastern Europe speaking a Slavic language.
- (UK, birdwatching) The Slavonian grebe.
Related terms 
- ^ John P. Maher (Chicago), "The Etymology of Common Slavic slověne 'Slavs'", (in:) Balkansko Ezikoznanie XIV, 2, p. 31–36, Sofia 1970