brooding vs preoccupation

brooding

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

adj
  • Broody; incubating eggs by sitting on them. 

  • Deeply or seriously thoughtful. 

preoccupation

noun
  • The state of being preoccupied or an idea that preoccupies the mind; enthrallment. 

  • The act of occupying something before someone else. 

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