back forty vs ends of the earth

back forty

noun

  • The most remote or inaccessible part of any place. 

  • The remote part of a farm. 

ends of the earth

noun

  • A very remote place. 

  • Extremities of the land. 

  • Distant land. 

How often have the words back forty and ends of the earth occurred in a corpus of books? (source: Google Ngram Viewer )