Indo-Aryanisation means to change someone's language from a previous language to an Indo-Aryan language.
In the northwestern Indian subcontinent, the stray Indo-Greeks, Hephthalites and Saka Scythians, became absorbed into the greater Indo-Aryan population of the subcontinent 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.
Three religious groups in Kerala, the Mappila Muslim 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.
The Parsi community, concentrated in Gujarat, are descendants of Zoroastrian refugees who fled from Greater Iran migrating into Gujarat, to fled from the Islamic conquest of Persia, since their religion was undergoing marginalization by Islam. These Zoroastrians began to lose their original language, adopting the local Indo-Aryan languages ex.(Gujarati), and have adopted many elements of the culture in Gujarat. Parsi is the preserved term for Farsi, since the Arabic phonology changed the P to a F. Thus Parsi directly means, Persian.
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.