Taboo
A prohibition on touching, saying, eating or doing something, backed by the belief that crossing the line brings harm.
Also: tabu, prohibition, ritual avoidance
The English word comes from Polynesian tapu, brought home from Tonga by Captain Cook's voyages. Anthropologists use taboo for a prohibition felt as more than mere custom: a danger believed to attach to the forbidden thing itself. Mary Douglas, in Purity and Danger (1966), argued that taboos often guard categories, so that things which fall between them, such as bodily fluids or hybrid animals, seem unclean. Sigmund Freud offered a different reading in Totem and Taboo (1913), now regarded as speculative. Taboos change over time and between cultures, and in everyday English the word has widened to mean any subject people avoid.