introversion vs restraint

introversion

noun
  • 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 turning inward 

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

restraint

noun
  • something that restrains, ties, fastens or secures 

  • control or caution; reserve 

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