'Appalachian' ultimately originates from the name of the 'Apalachee' people encountered by early Spanish explorers; the Spanish form was 'Apalachee', referring to a people and place on the Gulf Coast.

'Appalachee' appeared on 16th-century Spanish maps and reports; English speakers borrowed the name as 'Appalachia' and later 'Appalachian' to refer to the region and the mountain range, and then to inhabitants.

Initially it referred to a specific indigenous people/place ('Apalachee'); over time the term broadened to mean the mountain range, the surrounding region ('Appalachia'), and people from that region ('Appalachians').