1660s, from Persian Hindu (adjective and noun) "Indian," from Hind "India," from Sanskrit sindhu "river," specifically the Indus; hence "region of the Indus," gradually extended across northern India. The Hindu Kush mountain range is said to mean literally "Indian killer," and was said to have been the name given by the Persians to a pass where their Indian slaves had perished in winter, but this is likely folk etymology.