'Appalachia' ultimately originates from the name of the Apalachee people encountered by Spanish explorers; the Spanish form was recorded as 'Apalachee' (or 'Apalache'), which was applied to the region and mountains.

'Appalachee' (name of a Native American people) was used by Spanish explorers in the 16th century, entered European maps and accounts as forms like 'Apalaches'/'Appalaches' (Spanish/French), and later developed in English into 'Appalachia' to refer to the mountains and surrounding region.

Initially it referred specifically to the Apalachee people or the area associated with them; over time it broadened to denote the mountain range and the larger cultural/geographic region now called Appalachia.