hard nut to crack vs situation

hard nut to crack

noun
  • A situation, person, group, etc. which is difficult to overcome or deal with. 

  • A problem that is challenging to solve. 

  • Used other than figuratively or idiomatically: see hard, nut, crack. 

  • A place, opportunity, etc. to which it is difficult to gain entry. 

  • An amount that is difficult to finance. 

situation

noun
  • A difficult or unpleasant set of circumstances; a problem. 

  • A position of employment; a post. 

  • The combination of circumstances at a given moment; a state of affairs. 

  • The place in which something is situated; a location. 

  • Position or status with regard to conditions and circumstances. 

  • An outfit, garment, or look. 

  • An individual movie theater. 

  • The way in which something is positioned vis-à-vis its surroundings. 

How often have the words hard nut to crack and situation occurred in a corpus of books? (source: Google Ngram Viewer )