wendisch or windisch is old german name for slavs.
slav (sloven) is a "speaker", which either means speaker of a particular language, or a free adult member of a community (with right to speak in assembly – zbor) unlike otrok (not allowed to speak – a slave, or a child) and nemec (mute: not able to speak).
or both.
only three groups – slovenes, slovaks and slovjaks – still self-identify as slavs; these three are regional variations of the same ethnonym sloven (slav). the rest are barbarians  8)