flak vs forbearance

flak

noun
  • A public-relations spokesperson. 

  • Anti-aircraft shell fire. 

  • Adverse criticism. 

  • Ground-based anti-aircraft guns firing explosive shells. 

forbearance

noun
  • A refraining from the enforcement of something (as a debt, right, or obligation) that is due. 

  • Patient self-control; restraint and tolerance under provocation. 

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