nubilous vs understandable

nubilous

adj
  • Unclear. 

  • Cloudy, misty. 

understandable

adj
  • Capable of being accepted or excused under the circumstances. 

  • Capable of being understood; comprehensible. 

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