I find it interesting the Swedish uses the word "slav" for both slave and slav. It would be an interesting field of study to discover what terms the old norse people who conquered much of the eastern slavs used. Did they genuinely refer to the whole bunch of people as "the slaves," or is the current confusion just a linguistic accident?
Ah, what I should of course have realised was that the old Norse word for slave was "þræll" (ancestor of modern English "thrall"). I don't have the patience to look up the old Norse word for slav, if it is even known, but it's clear that they at least didn't refer to the Slavic peoples with the same word as for a slave (although they did take slavs as thralls), and the word has been replaced by a newer loan at some point in history.
A petition to bring back träl as the Swedish word for slave and end the confusion!