'Apayao' originates from the Isneg (Itneg) language, specifically the word 'apayaw', where 'apa' meant 'people' and 'yaw' referred to a place or river.

'apayaw' was recorded by Spanish colonizers and mapmakers as 'Apayao' during the colonial period, and this form became the modern English toponym 'Apayao'.

Initially, it referred to a local community or place in the indigenous language; over time it evolved into the formal name of the province in modern usage.