contingency vs surety

contingency

noun
  • An amount of money which a party to a contract has to pay to the other party (usually the supplier of a major project to the client) if he or she does not fulfill the contract according to the specification. 

  • The quality of being contingent, of happening by chance. 

  • A possibility; something which may or may not happen. A chance occurrence, especially in finance, unexpected expenses. 

  • A statement which is neither a tautology nor a contradiction. 

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. 

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