Final answer:
The word indicating a social outcast that originated from Tamil for a member of a low caste is 'Pariah.'. This term is related to the historical caste system in India.
Step-by-step explanation:
The word that originally comes from Tamil denoting a member of a low caste and today means a social outcast is Pariah. The caste system in India classified people into different groups such as Brahmins, Kshatriyas, Vaishyas, Sudras, and the Untouchables (Dalits). The Untouchables faced extreme poverty and were socially shunned, similar to the concept of a pariah today. Gandhi referred to the Untouchables as the "children of God" in his efforts to improve their status.