Rahr Plains is also known as Rahr Plains, Rarh Plain.Rarh region is a toponym for an area in the Indian subcontinent that lies between the Chota Nagpur Plateau on the West and the Ganges Delta on the East. Although the boundaries of the region have been defined differently according to various sources throughout history, today it is mainly coextensive with the state of West Bengal also comprising some portions of the state of Jharkand and Bihar in India.
The Rarh region historically has been known by many different names and has hosted numerous settlements throughout history. It is suggested that the Rarh region hosted an ancient civilisation also called Rarh and a powerful state, however much of its ancient history remains unknown.
The etymology of the word Rarh is not clear however there are many authors suggesting that it originates from a local language of Austroasiatic family. It could have originated from any of the following words of the Santali language; lar means “thread”, rarh means “tune” and larh means “snake”. And according to Sarkar, the word originates from Proto-Austroasiatic *Rāŗhā or *Rāŗho which means “land of red soil” or “land of laterite”.
Western parts of Rarh merging with the Chota Nagpur Plateau was historically called Vajjabhumi a definition demarcating it from the eastern part of Rarh which was called Subbhabhumi, Sumhabhumi or Suhmo. There are many descriptions of the geographical area called Rarh or Gangaridae, some being quite imprecise they are capable of indicating a very large area and some though being precise, differ in their descriptions. Most precise descriptions of Rarh seem coextensive with West Bengal. More imprecise descriptions denoting larger areas usually derive from Western sources describing Gangaridae. Some sources describe a smaller area while referring to Rarh as a geographical area and a larger description comes with Rarh defined as a geopolitical unit.
According to the Encyclopædia Britannica, Rarh is mainly Murshidabad’s surrounding region, a high, undulating continuation of the Chota Nagpur plateau to the West, and the Bagri, a fertile, low-lying alluvial tract, part of the Ganges (Ganga)-Brahmaputra delta, to the East. Banglapedia says that Rarh is consisted of a large part of West Bengal. And according to West Bengal Travel & Tourism Guide, the northeastern border of Rarh is located within Birbhum.
Historically, a statement in Digvijayaprakasha locates Rarh as from the north of the Damodar River and to the west of Ganges in the south. Even though earliest written documents divides Rarh as West Rarh and East Rarh, later documents starting from the 9th and 10th century AD, divides it to Daksina Radha (Northern Rarh) and Uttara Radha (Southern Rarh). However as inferred from later documents, this newer distinction (North/South) is not based on geography but two political states. Southern Rarh included different large settlements of the modern districts of Howrah, Hooghly and Burdwan in West Bengal, or considerable portions of West Bengal lying between the rivers Ajay and Damodar. The Ajay river is usually regarded as constituting the boundary line between Northern and Southern Rarh. Based on different epigraphic records, it is suggested that Northern Rarh included the western parts of the modern district of Murshidabad, the entire district of Birbhum, including some parts of Santhal Pargana, and the northern part of the Katwa sub-division of Burdwan district. There are many archaeological sites in many parts of Rarh, where studies are going on.