governor vs head of government

governor

noun
  • The chief executive officer of a first-level division of a country. 

  • A constituent of a phrase that governs another. 

  • A device which regulates or controls some action of a machine through automatic feedback. 

  • A member of a decision-making for an organization or entity (including some public agencies) similar to or equivalent to a board of directors (used especially for banks); a member of the board of governors. 

  • A pilot; a steersman. 

  • Father. 

  • Boss; employer; gaffer. 

head of government

noun
  • The chief officer of the executive branch of a government, often presiding over a cabinet; usually called Prime Minister (in a parliamentary system) or President (in a presidential system). 

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