introversion vs reluctance

introversion

noun
  • A turning inward 

  • Arrangement of two similar words, lines, etc. to form the middle part of a structure. 

  • The action of turning one's thoughts upon internal or spiritual matters. 

  • A personality orientation towards the self and mental abstraction; behavior expressing such orientation. 

reluctance

noun
  • Hesitancy in taking some action. 

  • That property of a magnetic circuit analogous to resistance in an electric circuit. 

  • Unwillingness to do something. 

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