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).
Urdu. n. 1. (Languages) an official language of Pakistan, also spoken in India. The script derives primarily from Persia. It belongs to the Indic branch of the Indo-European family of languages, being closely related to Hindi but containing many Arabic and Persian loan words.