During the medieval period (13th-16th century), the Morans as well as Chutias after coming in contact and becoming partially assimilated by the invading Shans, resorted to speaking the lingua franca, which was a mixture of their native tongue and Prakrit.
This process of transition gave rise to the Moran language, which over time was again replaced by a modern form of Assamese which had a greater influence of Prakrit.
They gradually migrated north from their original location to Tipam and Charaideo, where the first Tai immigrants met them; this move was probably due to spread of wet-rice cultivation.
[4] When the British arrived in the 19th century, the area between Dibrugarh and Sadiya was mostly virgin forests[5] and the chief habitat of the Morans.
[7] The Moran as well other Kacharis word for water is "Di", which apparently forms the first syllable of all major rivers of Upper Assam including Dibang, Disang, Dikhou, Dikrong, Dikarai, Dihing, Digaru, Difolu, Dimow, Disoi, and so on; this shows that the group were the dominant tribe in the entire region with their seat in Sadiya, the earliest known power and civilisation of Chutias.