Nihali is an endangered language spoken by about 2500 people in central India particularly in Jalgaon-Jamud tehsil of Maharashtra. Noteworthy is, it’s a language isolate (i.e. not belonging to any Indian language family even though surrounded by languages belonging to Munda, Indo-Aryan, & Dravidian language families).
Even though Nihali has heavily borrowed lexicon & structures from it’s neighboring languages like Korku (a Munda language), Marathi, Hindi & Dravidian Gondi, interestingly about 24% of Nihali vocabulary has no correspondences to whatever in India. That’s Nihali’s unique vocabulary.
For many of it’s neighboring language speakers, Nihali is like a secret language of Nihali people who call themselves Kalṭo. This may be due to the fact that Nihali speakers are mainly bilingual in Korku & Nihali, and use Nihali only to avoid other’s understanding in public.
Till now, no genetic relationship has been established yet with other language families of India, but some researchers have linked Nihali to languages such as Nostratic (Eurasian languages), Kusunda (of Nepal), and Ainu (of Japan). But all of these seem unreal. On the other hand Nihali could point to linguistic status of Ancient India