plausible vs understandable

plausible

adj
  • Obtaining approbation; specifically pleasing; apparently right; specious. 

  • Seemingly or apparently valid, likely, or acceptable; conceivably true or likely. 

understandable

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

  • Capable of being understood; comprehensible. 

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