How did the word "Zi" come from in the Three Kingdoms period?

Simply put, the names of the ancients mainly include surnames, first names and characters. Needless to say, surnames run in the family, names are taken by parents, and words are taken by the ancients themselves in order to walk around the rivers and lakes and make friends. For example, Zhao Yun, as you said, is Zhao Mingyun Zilong.

The meaning of "word" is mostly an extension or annotation of the meaning of "name".

When you humbly address your friends, subordinates or people, you address them in their own words.

But not everyone has something to say. Generally speaking, literati, nobles or people with at least a little education will have it.

For example, Liu Bang, the Emperor Gaozu, had no words because he was born in poverty and had no education. His friends directly call him Liu Bang or Liu Ji, and this "season" is not what he said, but because he ranks third in the family, and season means third.

Another example is Han Xin, who has nothing to say.

Zhang Fei's impression seems a little rough and vulgar, but it's just a fictional image in novels and legends. In fact, Zhang Fei is very literate and a calligrapher. So he also gave himself a word, Ji De. I think since we want to fly, we should let our wings fly in the moral direction. In the end, he didn't let us down.