capability vs strength

capability

noun
  • the power or ability to generate an outcome 

  • A digital token allowing a user or process to interact in a specified way with an object that is subject to access control. 

strength

noun
  • The intensity of a force or power; potency. 

  • The quality or degree of being strong. 

  • The strongest part of something; that on which confidence or reliance is based. 

  • A positive attribute. 

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