According to the Gentoo Wiki Localization guide, Just like in ja_JP where 'ja' is the language code for Japanese and 'JP' is the language code for Japan, what is 'zh' in zh_CN where 'CN' stands for China?
Well actually I was just bored and wanted to make a thread, it's written in the link in the Gentoo wiki article anyway.
zh stands for zhong/中, meaning middle. This devrives from the "steal translated webnovel" theory, where the ideology is to think that the person in question is in the middle of the universe and cannot be stopped so it's entirely okay to forcefully steal translated webnovels. Yet, this theory is obviously incorrect, therefore the CN is there instead of ZG or something. Yeah, I'm bored too.