Whilst the etymology of the word 'slave' may well come from the root 'slav', the slavic people were NOT the first slaves.
Slavery has been going on since pre-biblical times, it is, for instance, mentioned in the ancient babylonian code of Hammurabi. Also, slavery was practised in ancient egypt, and other middle eastern countries.
Apologies for not posting the text of the source....its in ancient akkadian cuneiform script, which I cannot read/write. I do know a little sumerian, but again, I cannot read it if written in cuneiform.