What's the history of Hinduism? Where did it originate and how did it spread?
Before we begin to understand the history of hinduism, it is necessary to define two important terms and their origins (For a short answer, please jump to the conclusion).
Hindu and Hinduism
The earliest reference to the term hindu comes from the one of the many Achaemenid royal inscriptions. An inscription found at Persepolis, the ceremonial capital of the Achaemenid empire, details the conquests of Darius the great. This Persian inscription dated approximately to 515 BCE lists "Hidus" as one of the Darius' conquests among others like Gandhara, Saka, etc.