Man of the world Tim Bowen returns with another idioms article that will do you the world of good.
The word world is used in a large number of idiomatic expressions. If someone (or something) is particularly important to you, you can say that he or she means the world to you. If that is the case, you probably think the world of him/her (like him or her very much).
If you are particularly experienced in life and not easily shocked by unusual or immoral behaviour you are a man or woman of the world. You might even have the world at your feet (be extremely popular or famous on the one hand, or have a lot of opportunities to do interesting or exciting things on the other). In the latter case, perhaps the world is your oyster (you can go anywhere or do anything that you like) and you might also set the world on fire (do something that creates a lot of interest or excitement). This expression is often used sarcastically, as in ‘She’s good but she’s not going to set the world on fire’.
If someone is in a world of their own, however, they do not realize what is happening around them because they are thinking about something else, as in ‘She was lost in a world of her own’ and, worse still, if they are not long for this world, they are euphemistically expected to die fairly soon.
Dead to the world does not mean ‘dead’, however. It means that someone is sleeping so deeply that it is almost impossible to wake them. Perhaps they need something that will do them the world of good (make them feel happier or healthier), as in ‘A holiday would do them the world of good’.