central vs on the edge

central

adj
  • Having or containing the centre of something. 

  • Being in the centre. 

  • Exerting its action towards the peripheral organs. 

  • Being very important, or key to something. 

noun
  • centre 

on the edge

prep
  • With figurative or temporal proximity to (an event, state of mind, etc.). 

  • In a state of excitement due to taking risks. 

  • In a precarious position, with one's recourses nearly exhausted. 

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