Rooted in religion and based on a division of labor, the caste system, among other things, dictates the type of occupations a person can pursue and the social interactions that she may have. Castes are an aspect of Hindu religion. Other religions in India do not follow this system.
-istan is a suffix in the Persian language (Farsi), denoting a place. Thus, Pakistan means place of the pure (pak=pure). It does not just refer to geographical areas, as in bimarestan=place of the sick=hospital. The suffix is widespread in Eurasia because of Persian influence (the Mughals of India for example used Farsi).
What is the meaning of Pakistan? Pakistan means land of the clean. It does not mean land of the pure, as some Pakistanis might fool you into believing, because pak means clean in Urdu and stan means land in Farsi, the i between pak and stan means of in Farsi and Urdu. In the languages of Pakistan and Iran the predicate always comes before the subject.