Meaning

noun a prejudice (especially in Polynesia and other South Pacific islands) that prohibits the use or mention of something because of its sacred nature

noun an inhibition or ban resulting from social custom or emotional aversion

verb declare as sacred and forbidden

originBorrowed from Tongan tapu (“prohibited, sacred”), from Proto-Polynesian *tapu, from Proto-Oceanic *tabu, from Proto-Eastern Malayo-Polynesian *tambu. Doublet of kapu. First attested in c. 1777. The p in the Tongan source was misheard as b.

Etymology from Wiktionary, CC BY-SA 3.0