Indo-Aryanisation is the process by which non-Indo-Aryan languages assimilate Indo-European linguistic features.
Indo-Aryanisation of Indo-Greeks, Indo-Hepthalites, Indo-Scythians
In North-West India, the stray Indo-Greeks, Hephthalites and Saka Scythians, became absorbed into the greater Indo-Aryan population of India when losing their own government being replaced by a successive empire. Many Indo-Aryan ethnic groups claim ancestry of these ancient peoples. Such Indo-Aryan ethnic groups being supposedly of such ancestry are most notably, the Punjabis, Sindhis, Rajasthanis and Gujaratis.
Indo-Aryanisation of Indian Arabs, Indian Africans, Indian Jews and Jewish origin groups
Three religious groups in Kerala, the MappilaMuslim community, who trace their origins to the Arab traders, the Nasrani Christians who trace their roots back to Syrian missionaries, and the Cochin Jewish communities who trace their origins to Jewish traders at the turn of the millennium in Kerala, underwent a process of Indo-Aryanisation as they were absorbed over time and adopted customs from their surrounding Indian community. The Indian African Siddi community in Karnataka who were brought to India originally by the Muslim rulers in 12th-13th century as military slaves, eventually worked up their way to the higher ranks in the armies of the Indian rulers and slowly assimilated into the local communities.
During the Muslim rule of the Northern and Northwestern Subcontinent, the rulers, who themselves were mostly of Turkic and Afghan origin, began to adopt the Indo-Aryan languages as their native tongue. For this reason many of these Turkic and Afghan rulers assimilated into Indo-Aryan speakers, thus many Indian Muslims today claim descent of these ancient peoples.
The Turco-Mongol Mughals initially spoke Chagatai, a Turkic language, then adopted Persian before adopting Urdu as their new native tongue.
Ahoms
Originally one of the Tai tribes, the Ahom people assimilated to Hinduism and other elements of Hindu culture after their migration to Assam and nearby regions. Gradually the Ahom language spoken by the tribe was replaced by Assamese, an Indo-Aryan language. As a result, the Ahom language is extinct as a spoken language and only used for ritualistic purposes.
Early Pashtun (Afghan) settlers in the Indian Subcontinent
Afghans came from Afghanistan and Afghania into India to claim a land called Rohillakand and then got assimilated ultimately adopting Urdu, forgetting Pashto, when being overruled by Mughals. Mughals and Pashtuns had an ancient history of bitterness. Pathan was an Indo-Aryanised version of the name Pashtun. Many Rohilla Pashtuns began inter-marriage with their neighboring Indian Muslims. To this reason, Pashto-Speakers of Afghanistan and Afghania will not consider them as Pashtuns, believing that they have very little Pashtun blood in them. Many Pathans will claim their pure Pashtun, due to the concept in Asia, that someones Paternal Lineage to determines their ethnicity, and even in the Pakhtunwali, ones father has to be Pashtun, when being determined an ethnic Pashtun. When in India, the Rohilla identity is present among Indian Muslims, but when moving into Pakistan, the identity strikingly decreases, as Rohillas consider the "Pakistani" identity instead of Rohilla. 30-35% of Muhajirs in Pakistan are likely Rohilla Pashtuns, but is likely to become absorbed into the central Pakistani culture. When claiming Afghan descent, would ultimately mean Pashtun, since the name in the past was an ethnic term and not a nationality, since the change of the name Afghan from ethnicity to nationality didn't happen until 50 years ago.
During the declaration of Hindi as an official language of India, many criticisms were received from some populations of India. Notably from Tamils. It was proposed that certain people feared to undergo language shift into Hindi. The Munda and Sino-Tibetan speakers also have a risk to become Indo-aryanised. "See also: Tamil Nationalism"