That is why In Indian subcontinent two distinct types of languages exist: A Sanskrit based language like Hindi,Urdu, Bengali,Maithili, Nepali and local Dravidian language like, Tamil Telugu, Jhagar etc. Upto that time almost all aryan were Hindu they had already stablished the caste system. Initially the man who performed rituals was Bahun and who served in military was Kshetriya and so on. But it became like heriditary. Just like a doctors son being a doctor and Engineers son being an Engineer.They also influenced Dravidian by Hindusim. But Muslism spred about 2000 years ago from Arab. Some Aryan changed to Muslim like most Pakistani but others remained Hindu. But about 700 years ago Muslim invaded India. Some Hindus changed to Muslim but some entered Nepal in search of safe place.At that time in the hill region there were other mongol loke race but in minority in western Nepal. In Kathmand it is very interesting. First Kirant(what kind of Kirant??still unknown) then Likshavi from India, then Malla from Rajasthan India ruled over the people. But who were the original people of Valley-still unknown.During Mall period more Hindu aryan entered the valley and developed the cast system.Pradhan, Shrestha and other Hindu dominated the Buddhist society. Some muslim also entered in valley.Malla being a pure Hindu from India developed Hinduism well in valley. That is why there are so many Hindu Temples.These Hindu mixed with the local people of valley to some extent . The locals of valley is believed to be Tibetian type people. Then a kind of language Newari developed by the mixture of Sanskrit and Tibetan type language. Some Malla king used to speak Urdu and Maithili as their language. Finally SAHa defeated Malla and some Malla went back to India and fled to hill area.