Taboo
2 of the 7 encyclopedias on this shelf carry an entry for Taboo. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
or TABU, from tapu, a Polynesian word, denoting an institution which was formerly in existence throughout Polynesia and New Zealand, but has now to a large extent disappeared before the spread of Christianity and civilization. The word signifies something set apart, either as consecrated or accursed, the idea of prohibition being conveyed in either case, whence the English word, taboo, i. e., forbidden. For example, in New Zealand the person of a chief was strictly taboo, and hence might not be touched; while the volcano Tongariro was taboo as being the supposed residence of demons, and even to look on it was at one time forbidden. The system seems to have had its origin in a superstitious dread of the unseen powers of evil, and the chiefs, quick to perceive the power which it would place in their hands, appear to have adopted it from remote times as a political engine, the priests readily co-operating with them for the sake of the influence which it gave them likewise. The chiefs were themselves amenable to the regulations of the taboo, but in a much less degree than their subjects, and possessed a wide discretionary power, which was limited only by precedent, of declaring objects to be taboo. The taboo could be removed only by the person by whom it was imposed, or by one greatly his superior in rank, but courtesy usually kept the latter power in abeyance. So potent was the superstition, that Scherzer states that among the Maoris even hostile tribes were in the habit of leaving unharmed all persons and things protected by the taboo. The idols, temples, persons, and names of the king were taboo (or sacred), and almost everything offered in sacrifice was taboo to the use of the gods. The prohibitions and requisitions of the taboo were strictly enforced, and every breach of them punished with death, unless the delinquent had powerful friends who were either priests or chiefs.
Aiton's Encyclopedia (1910)
among the Polynesians of the South Pacific, a practice of setting aside certain things as forbidden or sacred. "The Tahitians never repair or live in the house of one who is dead; that and everything else belonging to him is tabooed," says Spencer. Taboo, in such a case, is declared by common consent; it may be pronounced by a chief or a priest, or even by a private person, but with less effect. Some words may not be spoken; they are sacred, tabooed. A person may be placed under a ban, declared unclean, tabooed. The term has passed into our English vocabulary, but without the notion of awe. Thus we may taboo politics, or even taboo a person as one not to be mentioned or admitted to social intercourse.