The Persian and greek origins of hindu and indos
Interestingly the words hindu and Hinduism are not Sanskrit words. No hindu ever coined them. The hindus were even unaware of such a terminology for a very long time. While the foreign scholars of Greece and Persia made an occasional glance out of curiosity towards the lands that existed beyond the indus, the native Indians were busy in their own little world oblivious of the fact that they had very little in common with the outside world except perhaps in matters of commerce, governance and few other things. The earliest reference to the word hindu can be found in the avestha the sacred book of the Zoroastrians. The word hindu ush was also found at least in two inscriptions of king darius (early sixth century BC) whose empire said to have extended up to the borders of the river Sindhu. Subsequently the word was picked up by Herodotus and later by the Armenians. For several centuries, the words was used to denote the people of the subcontinent, not people of a particular faith. From the eighth century AD onwards when the muslims began to settle down in the indus region they started using the word hindus to distinguish the natives from the muslims.
The word hindu is a secular word
Thus, we can see that the word hindu was originally intended to refer to the native people of the indian subcontinent rather than to their religious identity. Hindustan was the land that existed beyond the river indus, and those that lived there were referred to as hindus. The word hindu was originally a secular word meant to define and distinguish the people of the indian subcontinent, rather than their religion. Accordingly, the land south of the indus river became identified as Hindustan. If we go by the ancient traditions there is hardly any difference between a hindu and an indian. Both the words were corrupt forms of the original Sanskrit word Sindhu meaning the river in general and the indus river in particular. The greeks referred to those living in the subcontinent as indos while the muslim scholars called them hindus. There was however one particular difference. The greek historians who called the subcontinent as indos hardly knew much about the religious beliefs and practices of the region, while the muslim scholars had some knowledge of them.
The hindoos of british raj
The Europeans who came to india from the sixteenth century onwards followed the same tradition and referred the natives as hindus to distinguish them from the non muslims. The british, who were until then referring the natives variously as natives, baniyans, heathens, gentoos, etc. started referring all the non muslim natives as hindoos. More than tradition, perhaps it was for convenience that they used the word to describe the non muslim population of india. Until then, the native people never identified themselves as hindus. It is doubtful whether they were even aware of it. According to gavin flood, the word hindu appears in the Sanskrit sources for the first time in the fifteenth century in Kashmir when the Shaiva historian srivara used it to distinguish muslims from non muslims. It appeared in the gaudiya Vaishnava texts in the sixteenth century to denote those who were not yavanas or the muslims. Among the scholars of the british period, raja rammohun roy was the first indian to use the word hindu in his writings in 1816. It was only during the 18th and 19th centuries that hindus started using the word to establish their national identity, oppose colonialism and imperialism and promote indian nationalism. They also found in it a convenient solution not only to distinguish their faith from islam and Christianity but also to counter and dispel any notion of superiority expressed or implied by the rival faiths. For the educated modern hindu of that period the word was a very convenient way to establish his identity against the british as well as the native muslims. For sometime the word Hinduism was used in a restricted sense to designate the vedic religion or Brahmanism. Nevertheless with the emergence of new reform movements which played a very crucial role in restructuring and redefining the social and religious traditions of the country, the word came to encompass the entire religious tradition that originated form the vedas and continued through centuries.