"A Chinese wall or ethical wall is an information barrier protocol within an organization designed to prevent exchange of information or communication that could lead to conflicts of interest. For example, a Chinese wall may be established to separate people who make investments from those who are privy to confidential information that could improperly influence the investment decisions. Firms are generally required by law to safeguard insider information and ensure that improper trading does not occur."

"Bryan Garner's Dictionary of Modern Legal Usage states that the metaphor title "derives of course from the Great Wall of China",[2] although an alternative explanation links the idea to the screen walls of Chinese internal architecture.[3]

The term was popularized in the United States following the stock market crash of 1929, when the U.S. government legislated information separation between investment bankers and brokerage firms, in order to limit the conflict of interest between objective company analysis and the desire for successful initial public offerings.[4] Rather than prohibiting one company from engaging in both businesses, the government permitted the implementation of Chinese-wall procedures."

https://en.wikipedia.org/wiki/Chinese_wall

though I still don't get the China reference, Great wall of China never really helped against any attacks or exchange of information, so I still don't get the etymology