compulsion vs hobby horse

compulsion

noun
  • The use of authority, influence, or other power to force (compel) a person or persons to act. 

  • An irrational need or irresistible urge to perform some action, often despite negative consequences. 

  • The lawful use of violence (i.e. by the administration). 

hobby horse

noun
  • A topic about which someone loves to talk at great length. 

  • A child's toy consisting of a (usually wooden or cloth) horse's head mounted on a stick. 

  • The Irish hobby, an extinct breed of horse. 

  • A puppet-like costume used in some traditional dances and festivals that gives its wearer the appearance of a man on horseback. 

  • An early bicycle with no pedals or brakes; a draisienne. 

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