|Vietnamese alphabet||húy kỵ|
A naming taboo is a cultural taboo against speaking or writing the given names of exalted persons in China and within the Chinese cultural sphere. It was enforced by several laws throughout Imperial China, but its cultural and possibly religious origins predate the Qin dynasty. Not respecting the appropriate naming taboos was considered a sign of lacking education and respect, and brought shame both to the offender and the offended person.
There were three ways to avoid using a taboo character:
Throughout Chinese history, there were emperors whose names contained common characters who would try to alleviate the burden of the populace in practicing name avoidance. For example, Emperor Xuan of Han, whose given name Bingyi (病已) contained two very common characters, changed his name to Xun (詢), a far less common character, with the stated purpose of making it easier for his people to avoid using his name. Similarly, Emperor Taizong of Tang, whose given name Shimin (世民) also contained two very common characters, ordered that name avoidance only required the avoidance of the characters Shi and Min in direct succession and that it did not require the avoidance of those characters in isolation.
However, Emperor Taizong's son Emperor Gaozong of Tang effectively made this edict ineffective after his death, by requiring the complete avoidance of the characters Shi and Min, necessitating the chancellor Li Shiji to change his name to Li Ji. In later dynasties, princes were frequently given names that contained uncommon characters to make it easier for the public to avoid them, should they become emperor later in life.
The custom of naming taboo had a built-in contradiction: without knowing what the emperors' names were one could hardly be expected to avoid them, so somehow the emperors' names had to be informally transmitted to the populace to allow them to learn them in order to avoid them. In one famous incident in 435, during the Northern Wei Dynasty, Goguryeo ambassadors made a formal request that the imperial government issue them a document containing the emperors' names so that they could avoid offending the emperor while submitting their king's petition. Emperor Taiwu of Northern Wei agreed and issued them such a document. However, the mechanism of how the regular populace would be able to learn the emperors' names remained generally unclear throughout Chinese history.
This taboo is important to keep in mind when studying ancient historical texts from the cultural sphere, as historical characters and/or locations may be renamed if they happen to share a name with the emperor in power (or previous emperors of the same dynasty) when the text was written. Thus, the study of naming taboos can also help date an ancient text.
Japan was heavily influenced by the naming taboo. In modern Japan, it concerns only the Emperor of Japan, whom people only refer as Tennō Heika (天皇陛下, his Majesty the Emperor) or Kinjō Heika (今上陛下, his current Majesty). Ancient Japanese people had so much respect for this custom that historians forgot the actual names of many historical figures or even sometimes the correct pronunciation, as many Han characters have multiple pronunciations. For example, the son of Oda Nobunaga, Oda Nobukatsu, is often called Oda Nobuo; but it mainly concerns more ancient historical figures like Murasaki Shikibu, whose actual name may forever remain a mystery.