ax to grind vs flack

ax to grind

noun
  • A proposition or point of view to advocate, especially motivated by self-interest. 

  • A grudge or grievance, with implications of confrontation. 

flack

noun
  • A publicist, a publicity agent. 

verb
  • To hang loosely; flag. 

  • To beat by flapping. 

  • To publicise, to promote. 

How often have the words ax to grind and flack occurred in a corpus of books? (source: Google Ngram Viewer )