The original meaning of "Old Keller" refers to a big gem, which has gradually become a proper name for a certain kind of people after years of changes. The word "carat" in English is what we call the weight unit of diamonds. One carat is equal to 200 milligrams. In old Shanghai, diamonds over 3 carats were very scarce and expensive. So whenever you can see such a "good thing" in a jewelry store, the old master in the store will give a thumbs-up and say,' This old Keller'. Later, this word was specially used to describe the old white-collar workers who came back from foreign countries. They have seen the world, and they have both modern consciousness and gentlemanly demeanor. They usually find a decent job in a foreign company. They earn a lot, so they dress well and have more pursuit of leisure life and culture.