reversal vs unpredictability

reversal

noun
  • A change in fortune; a change from being successful to having problems. 

  • An instance of reversing. 

  • The state of being reversed. 

adj
  • Intended to reverse; implying reversal. 

unpredictability

noun
  • The quality of being unpredictable. 

  • Something which is unpredictable. 

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