ownership vs tenure

ownership

noun
  • The state of having complete legal control of something; possession; proprietorship. 

  • Responsibility for something. 

tenure

noun
  • A right to hold land under the feudal system. 

  • A status of possessing a thing or an office; an incumbency. 

  • A period of time during which something is possessed. 

  • A status of having a permanent post with enhanced job security within an academic institution. 

verb
  • To grant tenure, the status of having a permanent academic position, to (someone). 

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