dictatorship vs iron fist

dictatorship

noun
  • A government which exercises autocratic rule. 

  • Any household, institution, or other organization that is run under such sovereignty or autocracy. 

  • A type of government where absolute sovereignty is allotted to an individual or a small clique. 

iron fist

noun
  • Ruthless and usually unrestricted control. 

  • Symbol of an army's tank or cavalry branch. 

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