not sure if you mean the geographical origin of the family name, or the meaning of the word. maybe this will help: although the centroid of Dendys (spelled variously Dendy, Dendys, Dendeys, Dendye, Dende) seems to have been in the Sussex/Surrey area of England (well-documented from the early 1500's), I have one source which states "...at Hayfield in the parish of Glossup in the county of Derby...was born about 1450 Otwell Dende or Dendye..." That's about 10 or 15 miles SE of Manchester.
Otwell's son William apparently began the move to Sussex/Surrey. Much Dendy history is found around the Dorking, Horsham, Ewhurst, Leigh area. Of course, the suffix "ing" in old english meant "place of". Therefore, Dorking was "place of dorks"(I hope you have the usual perverse Dendy sense of humor).