Aryan religion is a collective term for modern Hinduism, Zoroastrianism, Buddhism and Jainism, as conversion and initiation into them is believed to make one Aryan or Noble.
The Hindu usage of the term "Aryan" has its roots in a tribe of people who received initiation of the Navjote in Zoroastrianism or Vedic upanayanam. In Vedic Hinduism the Brahmin, Kshatriya, Vaishyas who recieved this initiation were also called 'Aryan.' This allowed them to attain spiritual perfection and self mastery. When an Aryan was called "pure", it meant spiritual purity.
In the Vedic religion, those who no longer received this initiation from Brahmin priests were considered "fallen" and were no longer considered "Aryan". This led to various movements like Buddhism and Jainism whose converts were also called 'Aryan' due to their purification rites through practice of meditation, self control and acts of virtue.