inviolable vs undownable

inviolable

adj
  • Incapable of being injured or invaded; indestructible. 

  • Not violable; not to be infringed. 

  • Not susceptible to violence, or of being profaned, corrupted, or dishonoured. 

undownable

adj
  • Invincible; which cannot be brought down or overcome. 

  • Undeniably important; which cannot be played down or ignored. 

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