inability vs spinelessness

inability

noun
  • Lack of the option to do something; powerlessness. 

  • Lack of the ability to do something; incapability. 

spinelessness

noun
  • The state or quality of being spineless (not having a spine (literally or figuratively)); cowardice. 

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