Nicholas Laughlin's blog etc.

"... there was no such thing as 'Hinduism' before the British invented the catch-all category in the early 19th century and made India seem the home of a 'world religion' that was as organized and theologically coherent as Christianity and Islam. The word 'Hindu' itself was first used by the ancient Persians to refer to the people living near the river Indus ('Sindhu' in Sanskrit). It later became a convenient shorthand for those who weren't Muslims or Christians.

"Certainly, most Hindus themselves felt little need for such self-descriptions, except when faced with blunt questions about religion on official forms. Long after their encounter with monotheistic Islam and Christianity, they continued to define themselves through their overlapping allegiances to family, caste, linguistic group, region, and devotional sect. Religion to them was more a matter of unselfconscious practice than of rigid belief; at any given time, both snakes and the ultimate reality of the universe were worshipped in the same region, sometimes by the same people. Religion very rarely demanded, as it did with many Muslims or Christians, adherence to a set of theological ideas prescribed by a single prophet, book, or ecclesiastical authority."

— Pankaj Mishra in the Boston Globe, examining modern Hinduism & its connection with nationalist ideology in India today.