Appalachian

in reference to the North American mountain range, c. 1600, Mountaynes Apalatsi; written apalachen by Spanish explorers and originally in reference only to the southern end of the range. Originally the name of the Apalachee, a Muskogean people of northwestern Florida, perhaps from Apalachee abalahci "other side of the river" or Hitchiti (Muskogean) apalwahči "dwelling on one side." The spelling shifted under influence of adjectives in -ian.