'Aquitanian' originates from Latin (via Medieval/Modern Latin), specifically the word 'Aquitanicus', where 'Aquitania' referred to the Roman province named for the Aquitani people ('land/people of Aquitania').

'Aquitanian' developed from Latin 'Aquitanicus' (Medieval/Church Latin), which itself derives from 'Aquitania' (the Roman provincial name), originally referring to the tribal name 'Aquitani'; the term entered English usage by way of medieval and modern scholarly/antiquarian Latin and French influences.

Initially, it meant 'of or belonging to the Aquitani or the Roman province of Aquitania'; over time it has come to mean more generally 'of or relating to Aquitaine' and is also used in historical/linguistic contexts to refer to the ancient people or language.