flare-up vs rending

flare-up

noun
  • A sudden intensification in activity. 

  • An inflammation such as of tendons (tendonitis) or joints (osteoarthritis). 

  • A sudden outbreak, outburst or eruption (originally of flame, but now used more generally of any violent activity or emotion). 

rending

noun
  • The act by which something is rent, or torn. 

How often have the words flare-up and rending occurred in a corpus of books? (source: Google Ngram Viewer )