diarchy vs realm

diarchy

noun
  • A state under the rule of two people; the form of government of such state. 

  • Rule by two people. 

realm

noun
  • A territory or state, as ruled by a specific power, especially by a king. 

  • A taxonomic rank in the phylogeny of viruses, higher than kingdoms. 

  • A scope of operation in networking or security. 

  • An abstract sphere of influence, real or imagined. 

  • An otherworldly dimension or domain — magical, ethereal, or otherwise — usually ruled or created by a mystical character. 

  • The domain of a certain abstraction. 

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