Why is Fang called Yuanling?

As an emperor, Li Shimin (Emperor Taizong) can't call his courtiers casually. Generally speaking, they are called Ai Qing, Ting Anne or Qing. If there are several courtiers, they are called "Qing et al." All ministers are called "courtiers" or "Manchu civil servants". A few ministers who are close to the emperor, or those who are interested in relying on and wooing the king, will call them by their first names (for example, "Ling Xuan"). The three of them were often called by the emperor, because the first two were the prime ministers of Emperor Taizong and were called "Du Fang", while Wei Zhi was a famous "minister who dared to give advice directly". As for the records in the history books, "Ling Xuan" was written as "Yuanling" for taboo. That is, when people name their names, they should not use the names of kings, temples, posthumous title, etc. Don't say a word. In addition, if this word is used in popular books and excerpts throughout the country, it should be replaced by other words (or similar pronunciation, or similar font, or one or two strokes reduced), including the classics of the previous generation. The word "Xuan" was taboo in the Tang Dynasty, and was the name of Emperor Kangxi (Michelle Ye) in the Qing Dynasty, so it was rewritten as "Yuan" in both dynasties, but not in other dynasties. Taboo words in past dynasties are also different. For example, during Xuan Di's reign, the book Xunzi was called Sun Tzu (not Sun Tzu's Art of War), and Xunzi himself was renamed Sun Qing. This is done to avoid the taboo of the emperor (named) ("Xun" is homophonic with "Xun").