ordeal vs trial by fire

ordeal

noun
  • A painful or trying experience. 

  • The poisonous ordeal bean or Calabar bean 

  • A trial in which the accused was subjected to a dangerous test (such as ducking in water), divine authority deciding the guilt of the accused. 

trial by fire

noun
  • Any ordeal which tests one's strength, endurance or resolve. 

  • A situation in which a soldier or other combatant faces the discharge of opposing weapons, as a test of their fortitude. 

  • A test in which a person is exposed to flames in order to assess their truthfulness, commitment, courage etc. 

How often have the words ordeal and trial by fire occurred in a corpus of books? (source: Google Ngram Viewer )