The Ao language is a Naga language spoken by the Ao Naga in Nagaland of northeast India, whose two varieties are nearly mutually unintelligible.
Mills (1926) lists the Ao Naga tribes of Nagaland as speaking three languages: Chungli, Mongsen, and Changki.
Changki Ao is spoken only in 3 villages - Changki, Japu and Longjemdang - which is poorly documented though reportedly related to Mongsen Ao.
Some Changki speakers can fluently converse in both Mongsen and Chungli, but a Mongsen Ao cannot speak Changki or understand it, whereas a Chungli can hardly understand or speak Changki.
[1] The speech of each Ao village has its own distinctive characteristics.