> It's not.

How is it not?

One of your other comments sounds like you agree with the etymology jefftk cited? But that says the exact same thing. The word slav was first, and the word slave was made from it.

Something being "propaganda" and "revenge" does not stop it from being the origin of a word.

Edit:

Oh, you elaborated slightly. > It's not derived, it's used - first by defeated.

That's what derived means. They took a word and used it to make a new word.

the other word is used in such way only as sounds similar to the second but has different meaning