The term 'Hindu' was derived from the river or river complex of the northwest, the Sindhu. Sindhu is a Sanskrit word used by the inhabitants of the region, the Aryans in the second millennium BCE. Later migrants and invaders, the Persians in the sixth century BCE, the Greeks from the 4th century BCE, and the Muslims from the 8th century CE, used the name of this river in their own languages for the land and its people.
The term 'Hindu' itself probably does not go back before the 15th and 16th centuries when it was used by people to differentiate themselves from followers of other traditions, especially the Muslims (Yavannas), in Kashmir and Bengal. At that time the term may have simply indicated groups united by certain cultural practices such as cremation of the dead and styles of cuisine. The 'ism' was added to 'Hindu' only in the 19th century in the context of British colonialism and missionary activity.
The origins of the term 'hindu' are now cultural, political and geographical. Now the term is widely accepted although any definition is subject to much debate. In some ways it is true to say that Hinduism is a religion of recent origin