dry-rot vs ripen

dry-rot

ripen

verb
  • To cause (something) to mature; to make ripe 

  • to grow ripe; to become mature (said of grain, fruit, flowers etc.) 

  • To approach or come to perfection. 

  • To mature; to fit or prepare; to bring to perfection 

How often have the words dry-rot and ripen occurred in a corpus of books? (source: Google Ngram Viewer )