I'm so glad that you've mentioned 'greenhand'! I've seen a number of Chinese members use this non-existent word here on italki, and I'm fascinated by it. While it's common for non-native users of a language to mistranslate or misapply the meaning of a real word, it is very rare indeed for an entire nation to use a word which no native speaker of that language has ever heard of.
As far as I can tell, Chinese speakers think that this word means 'beginner' or 'novice'. It doesn't. In fact, even 'green' doesn't have this meaning. 'Green', as an adjective, can mean innocent, in the sense of impressionable and gullible - it certainly isn't a synonym of 'novice'.
A 'hand' is an old-fashioned term for a worker, and in the 19th century there were some instances of referring to new members of ship's crews as 'green hands' - usually two words. A search took me to an text of the American writer Mark Twain using the term (again as two words) meaning an unskilled boat-handler. I wonder if some Chinese translator read this text and presumed that this was a common and general word for a novice. Then from there, did it somehow end up in dictionaries and textbooks - misleading millions upon millions of Chinese people into thinking that this was a normal English word? If so, it's a mistake of quite epic proportions.
Does anybody have any other ideas about how this colossal misunderstanding came about?