It was enforced by several laws throughout Imperial China, but its cultural and possibly religious origins predate the Qin dynasty.
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.
[4] 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.
[6] 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.