exigency vs preservation

exigency

noun
  • The demands or requirements of a situation. 

  • An urgent situation, one requiring extreme effort or attention. 

preservation

noun
  • The act of preserving; care to preserve; act of keeping from destruction, decay or any ill. 

  • The state of being preserved, how something has survived. 

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