invalid vs tenable

invalid

verb
  • To make invalid or affect with disease. 

  • To exempt from (often military) duty because of injury or ill health. 

adj
  • Not valid; not true, correct, acceptable or appropriate. 

  • Suffering from disability or illness. 

  • Intended for use by an invalid. 

tenable

adj
  • Fit for habitation, similar, or related use. 

  • Capable of being defended against assault or attack; defensible 

  • capable of being maintained or justified; well-founded 

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