'Araucanian' originates from Spanish, specifically the place-name 'Araucanía' (Spanish 'araucan(o)' used for people from that region), where 'Araucanía' referred to the region inhabited by the people Europeans called Araucanians.

The English word entered usage via Spanish in the 16th–17th centuries as 'Araucanian' (from Spanish 'araucan' / 'Araucano' and the placename 'Araucanía'), used in older English texts to denote the Mapuche people or their language; over time the ethnonym 'Mapuche' and the language name 'Mapudungun' became preferred.

Initially it meant 'of or belonging to the Araucanians (the people of Araucanía)' and later came to be used more broadly in English as an adjective referring to the region, people, or language; modern usage is now less common and often considered historical or specific.