impassable vs inviolable

impassable

adj
  • Incapable of being overcome or surmounted. 

  • Not usable as legal tender. 

  • Incapable of being passed over, crossed, or negotiated. 

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. 

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