egoism vs self-interest

egoism

noun
  • The tendency to think selfishly with exclusive self-interest in mind. 

  • Egotism (tendency to talk excessively about oneself). 

  • The belief that moral behavior should be directed toward one's self-interest only. 

self-interest

noun
  • One's personal interest or advantage, especially when pursued without regard for others. 

How often have the words egoism and self-interest occurred in a corpus of books? (source: Google Ngram Viewer )