immune vs obligated

immune

adj
  • Exempt; not subject to. 

  • Not vulnerable. 

  • Of or pertaining to the immune system. 

  • Protected by inoculation, or due to innate resistance to pathogens. 

noun
  • A person who is not susceptible to infection by a particular disease 

verb
  • To make immune. 

obligated

adj
  • having an obligation; obliged 

  • committed 

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