I've been doing research on Old Shanghai, during the 19th Century and early 20th Century. I know all about the Opium Wars and the Opium trade and their effect on the country. But I'm still not sure why one would call it "Whore of the Orient." Was it because of the country's addiction to opium during the time, the flood of European refugees, or just the city's popularity?
The easiest answer would be that the city was called a "whore" because of it's opium addiction, as though it's a "whore" for opium. But I want to make sure that this is the reason, and the term doesn't come from something unrelated.