The Munda languages are a group of 22 tribal languages spoken in East and Central India. The best known of these is Santali, with about eight million speakers. It is also the only one with official status at the national level. Mundari — spoken by the Munda tribe, which has given its name to the whole group — has just over one million speakers. The Ho language has about the same. A few of the others, such as Gutob and Turi, have so few speakers that they are seriously endangered.

These languages are not Indo-Aryan languages, like Hindi or Bengali. Neither are they Dravidian languages, like Tamil or Telugu. Nor yet are they Sino-Tibetan languages like Ladakhi, Mizo, or Bodo. They belong to a fourth family: the Austroasiatic languages, which includes faraway relatives like Vietnamese.

Most people who speak Munda languages have a traditional faith that bears little resemblance to Hinduism. Many instead call it Sarnaism or Sarna Dharam, a term which unifies the faith of the different tribes.

Bonga, in Sarnaism and related belief systems, is a general term for a supernatural entity. This includes deities, such as the creator god Sing Bonga (also known as Thakur Jiu), as well as ambivalent spirits, malevolent entities, and ghosts.

Anthropologists who have studied the Santals and other tribes have remarked on how believers do not talk much about the Bongako (the plural form) — partly out of fear of divine power, and partly because of the spirits’ unknowability. Furthermore, the deities of Sarnaism are not worshipped as idols, but in a sacred grove of sal trees, called the sarna sthal. As a result, there is little in the way of physical descriptions of these entities.