terrain vs umbworld

terrain

noun
  • The surface of the earth; the ground. 

  • A single, distinctive rock formation; an area having a preponderance of a particular rock or group of rocks. 

  • An area of land or the particular features of it. 

umbworld

noun
  • The surrounding world; the world or sphere about one; the environment. 

How often have the words terrain and umbworld occurred in a corpus of books? (source: Google Ngram Viewer )