
Dalit or Untouchable Woman of Bombay according to Indian Caste System - 1942 - Wikimedia Commons
Throughout history and throughout the world, there have been classes of untouchables. Best known perhaps (other than Elliott Ness and Wall Street bankers) are the caste that goes by the name in South Asia, a.k.a. the Dalits, but there are/were also for instance the Cagots in France, the Burakumin in Japan, and the Roma and Jewish populations in medieval Europe though the Middle East. In the US, one could include the black and native populations. Wikipedia has this definition:
Untouchability is the social-religious practice of ostracizing a minority group by segregating them from the mainstream by social custom or legal mandate. The excluded group could be one that did not accept the norms of the excluding group and historically included foreigners, house workers, nomadic tribes, law-breakers and criminals and those suffering from a contagious disease. [More...]