prop up vs reinforce

prop up

verb
  • To support with, or as if with, a prop. 

  • To be at the bottom of (a league) 

reinforce

verb
  • To emphasize or review. 

  • To strengthen, especially by addition or augmentation. 

  • To encourage (a behavior or idea) through repeated stimulus. 

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