The word “Hindu” denotes more than a set of theological beliefs. In many languages, French and Persian among them, the word for Indian is Hindu. Originally foreigners used it when referring to the people beyond the Indus River, which is now in Islamic Pakistan. In fact, the word Hindu did not exist in any Indian language until its use by outsiders gave Indians a term for self-definition. Many Hindus, in other words, call themselves by a label that they didn’t invent but adopted cheerfully.

“Hinduism,” then, is the name that...