Vayu language

Vayu (वायु), Wayu or Hayu (हायु) is a Sino-Tibetan language spoken in Nepal by about 1740 people in Province No. 3. Dialects include Sindhuli and Marin Khola.
The Vayu language features SOV ordering. There are strong Nepali influences in its phonology, lexicon, and grammar. Its writing system uses the Devanagari script. There are no known monolingual speakers of the language, as its speaking population also uses Nepali. Despite a lack of monolingual children, use of Vayu has survived into the 21st century 
Geographical distribution.
Vayu is spoken in the following locations of Nepal.
Vayu is spoken in the Sun Koshi valley, southwards across the Mahabharat range. Ethnic Vayu live on the hills on both sides of the Sun Kosi River but the language is only spoken in the villages listed.
Further reading.
Hodgson, B. (1857). Váyu Vocabulary. "Journal of the Asiatic Society of Bengal 26." 372-485.
Hodgson, B. (1858). On the Vayu tribe of the Central Himalaya. "Journal of the Asiatic Society of Bengal 27." 443-6.
Michailovsky, B. (1973). Notes on the Hayu language. "Kailash : A Journal of Himalayan Studies, 1(2)", 135-152.
Michailovsky, B. (1974). Hayu Typology and Verbal Morphology. "Linguistics Of The Tibeto-Burman Area", 11-26.
Michailovsky, B. (1976). A Case of Rhinoglottophilia in Hayu. "Linguistics Of The Tibeto-Burman Area", 2293.
Park, I. (1995). Grammaticalization of Verbs in Three Tibeto-Burman Languages. "Dissertation Abstracts International, 55(8)", 2369A.
Sherard, M. (1986). Morphological Structure of the Pronominal and Verb Systems in Two Pronominalized Himalayan Languages. In J. McCoy, T. Light (Eds.) , "Contributions to Sino-Tibetan Studies" (pp. 172–199). Leiden: Brill.
Yadava, Y. P., Glover, W. W. (1999). Topics in Nepalese Linguistics. In Yadava, Yogendra P. and Warren W. Glover (eds.) Kamaladi, Kathmandu: Royal Nepal Academy. p. 603.