I'm not sure, Shona, but here's what Atomica has to say:
pa·ri·ah (pə-rī'ə)
n.
1. A social outcast: “Shortly Tom came upon the juvenile pariah of the village, Huckleberry Finn, son of the town drunkard” (Mark Twain).
2. An Untouchable.
[Tamil paṛaiyar, pl. of paṛaiyan, pariah caste, from paṛai, festival drum.]
WORD HISTORY The word pariah, which can be used for anyone who is a social outcast, independent of social position, recalls a much more rigid social system, which made only certain people pariahs. The caste system of India placed pariahs, also known as Untouchables, very low in society. The word pariah, which we have extended in meaning, came into English from Tamil paṛaiyar, the plural of paṛaiyan, the caste name, which literally means “(hereditary) drummer” and comes from the word paṛai, the name of a drum used at certain festivals. The word is first recorded in English in 1613. Its use in English and its extension in meaning probably owe much to the long period of British rule in India.
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The American Heritage® Dictionary of the English Language, Fourth Edition
