hang-up vs monkey wrench

hang-up

noun
  • An unforeseen obstacle to progress; a hitch or delay. 

  • An emotional difficulty or a psychological inhibition; a complex. 

monkey wrench

noun
  • An unexpected or troublesome problem, obstacle or dilemma. 

  • A wrench (spanner) with an adjustable jaw. 

How often have the words hang-up and monkey wrench occurred in a corpus of books? (source: Google Ngram Viewer )