long shot vs one in a million

long shot

noun
  • Something unlikely; something that has little chance of happening or working. 

  • A master shot, the primary wide shot of a scene into which the closeups will be edited later. 

  • A shot fired at a distant target. 

one in a million

noun
  • Something extremely rare or unlikely. 

How often have the words long shot and one in a million occurred in a corpus of books? (source: Google Ngram Viewer )