brooding vs introversion

brooding

noun
  • A spell of brooding; the time when someone broods. 

adj
  • Broody; incubating eggs by sitting on them. 

  • Deeply or seriously thoughtful. 

introversion

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

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

  • A turning inward 

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

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