Hinduism is a word that is widely misinterpreted and misused. A lot of people are unaware of the word's origins. Certain politicians in India either support or oppose a particular ideology or political party by using the terms Hindu and Hindutva with connotations of community. Hindus and Hinduism are terms used to describe a group of people who follow a particular religion to the rest of the world.
It is a truth that the terms "Hindu" and "India" originate from outside of India. The term "Hindu" is neither derived from Sanskrit, nor is it present in any of the regional dialects or languages spoken in India. It should be mentioned that the word "Hindu" is in no way religious. The term "Hindu" does not appear in any of the Old Vedic texts.
It is said that the Persians used to refer to the Indus river as Sindhu. Indus is a major river which flows partly in India and partly in Pakistan. However, the Persians could not pronounce the letter "S" correctly in their native tongue and mispronounced it as "H." Thus, for the ancient Persians, the word "Sindhu" became "Hindu." The ancient Persian Cuneiform inscriptions and the Zend Avesta refer to the word "Hindu" as a geographic name rather than a religious name. When the Persian King Darious 1 extended his empire up to the borders of the Indian subcontinent in 517 BC, some people of the Indian subcontinent became part of his empire and army. Thus for a very long time the ancient Persians referred to these people as "Hindus". The ancient Greeks and Armenians followed the same pronunciation, and thus, gradually the name stuck.
The word "India" also has a similar foreign origin. Originally, the native Indians used to address the Indian subcontinent as "Bharat". As a matter of fact in Mahabharat,which is one of the two "Itihasa", we find reference of the word "Bharat". As per legend, the land ruled by the great King "Bharata" was called Bharat.
The ancient Greeks used to mispronounce the river Sindhu as Indos. When Alexander invaded India, the Macedonian army referred to the river as Indus and the land east of the river as India. The Greek writers who wrote about Alexander preferred to use the same name.
For the Arabs the land became Al-Hind. The Muslim rulers and travelers who came to India during the medieval period referred the Indian subcontinent as "Hindustan" and the people who lived there as Hindus.
Thus, if we go by the original definition of the word Hindu, any person living in the land beyond the river Indus is a Hindu and whatever religion he or she practices is Hinduism, the word Hindu is a secular word. Hinduism denotes any religion or religions that are practiced by the people living in the Indian subcontinent.