One thing that opinion polls of what people think of various countries miss is the matter of salience. It's easy to get into a row about the United States because people care one way or another about what it does. People who know that I'm intererested in China think of it as a hobby. I'm that bloke who's interested in China, as opposed to stamp collecting or comics or whatever it may be. When Bo Xilai got busted and it made the news in the UK I was asked in a casual way what all that was about, then. I mentioned CDIC, which I said was a kind of police force that just investigated politicians and officials. A bit like the British Transport Police, only with politicians, not transport. Everyone thought that was a really good idea - China, eh? They know what they're doing, that lot - and then we had another drink and talked about something else.
Anyway, that bit of rambling aside and more for the record than anything else, Caixin has a nice rundown of the structure and personnel of China's discipline inspectors. As we can see, they're not really like the British Transport Police. I would guess that ultimately their historical origins lie in the attempts of various Tsarist era Russian revolutionary organisations to evolve structures that would enable them to resist penetration by the Okhrana, formalised in post revolutionary Bolshevik practice, and, perhaps, transmitted to China through Mao's security chief Kang Sheng, who had a ringside seat at the Yezovzshchina.
That's guesswork. Worth noting at the link is the fact that a lot of the current CDIC structures were put into place under Hu Jintao, which tends to the conclusion that the impetus for Xi's purge has been building for a while and represents a genuine movement within the Party. I've read elsewhere that one of the first things that Wang Qishan did when he became head of the discipline inspectorate was to change its funding structure so that CDICs local organs were paid by central rather than provincial governments. Thus, the cossacks were able to work for the Tsar.