I have come across the phrase 'not long for this world' in many English novels, but it has always struck me as odd, as if a word or part of the sentence were missing. I visited numerous websites but all seem to focus on what the phrase means (I knew what the phrase meant already from context in the novels), not its structure, in particular the, in my eyes, odd use of 'long for'.
I am not sure if this is the right place to be asking this particular question, but where does 'long for' come from in this sentence? Is it some archaic use or form of 'belong'?
Thanks for any light you can shed on this!