What do you mean by "an iron official and a flowing official"?

It means: yamen has existed like iron for a long time; Officials are like running water, changing all the time. Metaphor cadres often change.

Usage:

Example 1: Teacher Yu said to me, "It is impossible to get President Yang's permission alone. As the saying goes, an iron-clad official can't guarantee that he will be the principal here all his life. "

Ex. 2: As the saying goes, an iron official is a flowing river. Our headmaster has changed six times in the past five years.

The origin of yamen;

In the past, it was called yamen. In fact, yamen was transformed from "yamen".

In ancient times, the sharp teeth of wild animals were often used to symbolize strength. "Yamen" is an ancient military term and another name for the gate of a military camp. At that time, wars were frequent, and the king ruled and defended the country entirely by force, so he paid special attention to military generals. Officers are proud of this and often put the claws and teeth of wild animals in their offices.

Later, because of trouble, it was carved into large animal teeth by wood outside the military camp, and there was a flagpole with animal teeth at the end and the edge cut into teeth. Therefore, Yingmen is also called "Tooth Gate" figuratively.

"Official's son" was originally an official position that prohibited officials from holding office. In the Tang Dynasty, the official's son was called "official's son", just like "prince" and "son". The "official's son" in Yuan Dynasty's zaju is an allusion to Mongolian officials at that time, including kings, dignitaries and powerful ministers in Yuan Dynasty.

They oppress the people, collude with the government and wealthy families, interfere in civil affairs, rob people's property or good women, and are annoying and fearful people. In the zaju, such a powerful figure was mercilessly exposed and satirized.