Koch[aka Koc, Kocch, Koce]
"[T]he Tintekiya Koch tend to live in villages where the majority of people are Tintekiya Koch, so at least within their villages their language is dominant. It is likely that Tintekiya Koch in Bangladesh will also be increasingly influenced by Bangla, but this influence will be slighter, and the rate at which Tintekiya Koch changes will likely be slower." (p. 25)
Bangla (official language); Garo; Hajong
In Bangladesh, Koch is used dominantly in daily life between the Koch except for the official domains, and occasions like worship, interacting with non-Koch speakers and in the marketplaces.
the plains of Sherpur district in Dhaka division, mostly near the Indian border.
30,000 speakers in India, and 6,000 in Bangladesh.
Bengali; Assamese; Garo; English; Hindi; Hajong; Rabha; Bora; Nepali
Meghalaya, West Garo Hills District; Assam, Goalpara, Nagaon districts; Tripura; West Bengal; Bihar. Also in Bangladesh.