egocentrism vs megalomania

egocentrism

noun
  • The constant following of one's egotistical desires to an extreme. 

megalomania

noun
  • A psychopathological condition characterized by delusional fantasies of wealth, power, or omnipotence. 

  • An obsession with grandiose or extravagant things or actions. 

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