surety vs turning point

surety

noun
  • A promise to pay a sum of money in the event that another person fails to fulfill an obligation. 

  • One who undertakes to pay money or perform other acts in the event that his principal fails therein. 

  • A substitute; a hostage. 

  • Evidence; confirmation; warrant. 

  • Certainty. 

  • That which makes sure; that which confirms; ground of confidence or security. 

turning point

noun
  • A crossroads. 

  • A T-junction. 

  • A decisive point at which a significant change or historical event occurs, or at which a decision must be made. 

  • A maximum or minimum on a graph. 

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