act of terrorism vs terrorism

act of terrorism

terrorism

noun
  • The system of fear and intimidation put into place during the Reign of Terror in Revolutionary France around 1793-94. 

  • The use of unlawful violence against people or property to achieve political objectives. 

  • The use of intimidation or bullying tactics. 

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