'Slave' is from 'Slav' — mass enslavement of Slavic peoples made the ethnic name mean bondage.
A person who is the legal property of another and is forced to obey them; a person who is excessively dependent upon or controlled by something.
From Old French 'esclave,' from Medieval Latin 'sclāvus' (slave), originally 'Sclāvus' (a Slav). During the early medieval period, vast numbers of Slavic peoples were captured and enslaved by Frankish, Germanic, and Byzantine raiders, as well as by the Arab slave trade. So many Slavic captives flooded the slave markets of medieval Europe and the Muslim world that the ethnic name 'Slav' became synonymous
The Latin word for slave was 'servus' (which gave us 'servant,' 'serve,' and 'service'). When 'sclāvus' replaced 'servus' in medieval usage, it was because the mass enslavement of Slavic peoples in the early Middle Ages was so extensive that an ethnic name became a generic term for human bondage — a linguistic scar that endures in nearly every European language.