Rangpuri is a Indic language spoken by ten million Rajbongshi people in Bangladesh, and five million in India, where they are known as Rajbanshi. Many are bilingual in either Bengali or Assamese. There is a strong language movement in West Bengal.

Rangpuri goes by numerous names. In Bangladesh, these include Rangpuri, Bahe Bangla, Anchalit Bangla, Kamta, Polia. In India, there is Kamtapuri,Dutta,Rajbangsi, Rajbansi, Rajbanshi, Rajbongshi, Goalparia, Koch Rajbanshi. Another name of the language is Tajpuri.

The main dialects are Western Rajbanshi, Central Rajbanshi, Eastern Rajbanshi and Hill Rajbanshi (also known as Koch language).

The Central dialect has the majority of speakers and is quite uniform. There are publications in this language. The Western dialect has more diversity. Lexical similarity is 77 to 89% between the three dialects. The version spoken in the hills has some influence of the local tribal languages and differs quite a bit from the other three. Rajbonshi shares 48 to 55% of its vocabulary with Bengali, and 43 to 49% with Hindi and Nepali.

Song In (in hangul 송인, in hanja 宋仁) was a civil official in the mid-Goryeo era who became the intermediary founder of the Jincheon Song clan. His highest post was munha pyeongjangsa (문하 평장사). This was the highest government position in the period. Song In was responsible for administration, judicial affairs and economy in the district.

As he performed meritorious deeds during the King, he was conferred with Chanhwagongsin and Jincheonbaek. Baek was a position of politicians who were responsible for administration, judicial affairs and economy in the district. As the government created him Jincheonbaek, his family started regarding Jincheon as their origin. Hence, the family origin became Jincheon Song.

When he was in the position of Sangsanbaek, he tried to be just and fair in all the administrative affairs and strived to enhance the welfare of his people. He also focused on education for the youth and courtesy for people, which made his district famous for most excellent behaviors in the nation. After that, the people have long paid tribute to his feats.