1. What is a interchangeable word?
"General departure" means "general use and metonymy", and replace this word with words with the same or similar pronunciation. (Words replaced by common names are called "original words". )
The "anti-Tang" you mentioned is a typical example. "Anti" and "Gui" are the same, and their sounds are synonymous. It first came from Touch the Dragon and Tell the Queen Zhao, and Don't rebel (don't let her come back).
Second, why are there interchangeable words?
1, the ancients often recorded according to the sound when recording. For example, The Analects of Confucius was not written by Confucius, but a "lecture record" of his students.
Concise Dictionary of Ancient Chinese contains more than 8,500 commonly used words in ancient Chinese and words that are not commonly used but are found in important ancient books or masterpieces (excluding variant characters).
It is conceivable that it took thousands of words to create it after so many years, and the ancients paid attention to simplicity and clarity. Listen and write it down. Is it easy to write wrong words? Not to mention many people deliberately follow the trend.
2. After burning books and burying Confucianism, almost all the ancient books were burned out. In the Han Dynasty, quite a few books were rewritten by some scholars' recitation and memory. Because the reciter at that time only remembered the pronunciation, but not the font, the writer often recorded the same word in different forms because of the differences in dialects or the influence of his education level.
Step 3 avoid it. It's a little complicated, just give a simple example-
There is a story in Lu You's Notes on the Old Learning Temple: a state official named Tian Deng, his subordinates and people in the state are not allowed to call his name or write his name. On the fifteenth day of the first month, turn on the lights for three days as usual. The little official who wrote the notice did not dare to write the word lamp, but changed it to "the state government set fire to it for three days according to law." This led to the joke that "only state officials are allowed to set fires, and people are not allowed to light lamps". (Actually, Tian Deng is a good official. )
PS: A headache for Chinese language and literature majors. Ordinary people just read stories. Appendix:
In 2 19 AD, Cao Cao was stationed in Baigukou, Hanzhong to plan state affairs. When he saw the water rushing down the Baohe River, he hit a stone and wrote the word "autumn snow", and his entourage reminded him that "Qiu Zi is short of water". Cao Cao clapped his hands and said with a smile, "Is a river short of water?" It has become a beautiful talk through the ages. Later, it was carved on a boulder in the river and has been passed down to this day.