Bihari languages were once mistakenly thought to be dialects of Hindi .
Languages have been more recently shown to be descendant of the language of the erstwhile Magadha kingdom -- Magadhi Prakrit , along with Bengali and Oriya .
Bihari languages were once mistakenly thought to be dialects of Hindi , but they have been more recently shown to be descendant of the language of the erstwhile Magadha kingdom -- Magadhi Prakrit , along with Bengali and Oriya .