This is a contact zone rather than a language region, and one of its languages was effectively made here. Sadri — a Bihari-derived speech from the Chota Nagpur plateau — travelled with the labour recruitment of the nineteenth century and became the common language of the gardens, because a workforce assembled from Kurukh, Mundari, Santali, Kharia and half a dozen other mother tongues needed something to share. Around the gardens sits Rajbanshi, the Indo-Aryan speech of the older cultivating population, which shades east into the Goalpara dialects of Assam and is claimed by some of its speakers as a language and by others as Bengali. Above and within, Nepali carries down from the ridge; Bengali and Hindi run the schools, the courts and the markets; and Mech, Rabha and Toto hold on in a small number of villages each.
Rajbanshi (Kamtapuri)Indo-Aryan, Eastern
Distinguished from standard Bengali by its vowels, its pronoun forms and a large agricultural and riverine vocabulary. It is recognised in West Bengal's list of official languages, and it is the language of Bhawaiya and Kushan gan.
बोलने वाले: Millions across this belt and adjoining districts, though census returns vary with how the question is asked
Sadri (tea-garden Sadri, Baganiya)Indo-Aryan, Bihari group
A contact language rather than an ancestral one for most of its speakers. It has absorbed Bengali, Nepali and Hindi vocabulary here and Assamese vocabulary further east, so the garden Sadri of the Dooars and that of upper Assam have already begun to diverge.
बोलने वाले: The working lingua franca of the tea belt on both sides of the Assam border
Kurukh, Santali and MundariDravidian (Kurukh) and Austroasiatic, Munda (Santali, Mundari)
The mother tongues that came with the recruitment, still spoken at home in many garden villages and used in ritual even where daily speech has shifted to Sadri. Kurukh is Dravidian — a Dravidian language spoken at the foot of the Himalaya, which is a direct trace of the migration.
Mech and RabhaSino-Tibetan, Bodo-Garo
Bodo-Garo languages of the forest fringe, closely related to the Bodo of the Brahmaputra valley. Both are under pressure from Bengali and Sadri and are strongest in the ritual register.
TotoSino-Tibetan, Himalayish
Spoken by one small community at Totopara at the foot of the Bhutan hills, and among the most restricted languages in India by number of speakers. It was written in Bengali script until a dedicated script was developed for it, which was encoded in Unicode in 2021.
Bengali, Nepali and HindiIndo-Aryan
Bengali in the towns and the schools, Nepali across the Terai and the garden fringes, Hindi as the market and transport language. Most people here operate in three or four languages daily and do not consider it remarkable.