Where did the last name ritter come from?

Ritter is a German occupational surname for a knight, a horseman, or a cavalryman. It is derived from the Middle High German word "ritter" (modern German "Ritter"), in turn from Old High German "ritari", which derives from Latin eques, "horseman, knight", "cavalryman". The term "eques" was derived from Proto-Indo-European *h₁ekwos, meaning "horse" (also the root for the word equine).