crossable vs impassable

crossable

adj
  • Able to be crossed. 

impassable

adj
  • Incapable of being overcome or surmounted. 

  • Not usable as legal tender. 

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

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