Bodo-Kachari, or just Kachari, is a generic term applied to a number of ethnic groups, predominantly in Assam, speaking Tibeto-Burman languages or claiming a common ancestry. The Bodo people are the descendants of the ancient Kirat people. Bodos are related to other Kirati groups from Nepal namely the Rai, the Limbu, the Jirel, the Yakkha, the Dhimal, the Thami,the surel, the hayu, the tharu, the sunuwar and others.
In ancient times, it is mentioned Assam as part of Kiratdesh. Kiratdesh is the land where early Kiratas dwelt. This estate includes the Entire Northern Eastern parts of India, including West Bengal, Assam, Tripura, Arunachal Pradesh, Bihar, Nepal, Bhutan, and some parts of Orissa. Bodo is derived from Bod which means Tibet and Kachari are derived from Kachar meaning area near the river.
They are considered to have reached the Brahmaputra valley via Tibet and settled in the foothills of the eastern Himalayan range which includes the whole of Assam, Tripura, North Bengal and parts of Bangladesh. That the Bodo-Kacharis were early settlers of the river valleys is taken from the fact that most of the rivers in the Brahmaputra valley today carry Tibeto-Burman names — Dibang, Dihang, Dikhou, Dihing, etc. — where di- means water in Dimasa language.(“Ti/twi”-Tripuri language,”Dwi” in boro & “Chi” in garo)