Sanskrit Sacred texts are Apauruṣeya, a word routinely and literally interpreted as ‘Not authored by human’, that is, like the Koran or the Bible, it is the direct ‘Word of God’.
That is not what the word is meant to suggest. Apauruṣeya denotes something not ‘Man-Made’, that is not a creation of a Modeled-Interpretation, a delineation extended in the Sruti/Smriti distinction below.
The Kanchi Paramacharya [1894-1994], holder of the lineage-seat of Śaṅkarācārya and a modern authority on the subject, explains that the proper name for Hinduism is simply as the ‘Nameless’. Vishnu has a thousand names [Sahasranāmam] precisely because Vishnu is Nameless.
The word ‘Nameless’ is simultaneously a name and a noun and an adjective about itself as a name and a noun. A meta-statement, a self-referential swivel.
Is ‘Nameless’ a name? Or is it not a name? [Try it.] ‘Nameless’ is a Self-Eating Expression. And the Symbol ‘0’ is the paradigmatic Self-Eating Expression.
The Paramacharya, a noted Sanskrit scholar and a descendent in its long literary traditions, was speaking as a Brahmin Intellectual. In its broadest sense, there is nothing that does not come under the aegis of Hinduism, from the physicality of yogic traditions and ecstatic devotional to radical atheism, from ritualistic celebration of sacred dates and places to nature ‘cults’, Tantric midnight orgies and graveyard rites. [‘The Freedom To Speak‘]
But the first temples, places of public worship, did not originate till well past the 200 CE. And most of the Puranic deities now venerated in their sanctum sanctorums did not take full form till 600 CE or thereabouts. The same goes for the standard lay-out of rituals although the chants date back to earlier times.