An Etymological Dictionary of the German Language/Sklave
Sklave, m., ‘slave,’ from late MidHG. slave, sklave, m., ‘slave,’ prop. ‘a captive of war.’ Derived from the national designation Slave (MidLat. Sclavus, Slavus) during the G. war of annihilation against the Slavs. AS. wealh, ‘Celt’ and ‘slave,’ is similarly derived. The G. word Sklave passed into other Teut. and Rom. languages; comp. Du. slaaf, E. slave, Fr. esclave, Ital. schiavo.