hard nut to crack vs hitch

hard nut to crack

noun
  • A problem that is challenging to solve. 

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

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

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

  • An amount that is difficult to finance. 

hitch

noun
  • A problem, delay or source of difficulty. 

  • A fastener or connection point, as for a trailer. 

  • A large Californian minnow, Lavinia exilicauda. 

  • A sudden pull. 

  • A period of time spent in the military. 

  • Any of various knots used to attach a rope to an object other than another rope. 

  • A hidden or unfavorable condition or element. 

verb
  • To strike the legs together in going, as horses; to interfere. 

  • To attach, tie or fasten. 

  • To pull with a jerk. 

  • To marry oneself to; especially to get hitched. 

  • To become entangled or caught; to be linked or yoked; to unite; to cling. 

  • To move interruptedly or with halts, jerks, or steps; said of something obstructed or impeded. 

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