complication vs felicity

complication

noun
  • A person who doesn't fit in with the main scheme of things; an interloper. 

  • The state of being complicated; intricate or confused relation of parts; complexity. 

  • The act or process of complicating. 

  • A feature beyond basic time display in a timepiece. 

  • A disease or diseases, or adventitious circumstances or conditions, coexistent with and modifying a primary disease, but not necessarily connected with it. 

felicity

noun
  • Something that is either a source of happiness or particularly apt. 

  • An apt and pleasing style in speech, writing, etc.; (countable) an apt and pleasing choice of words. 

  • Happiness; (countable) an instance of this. 

  • Reproduction of a sign with fidelity. 

  • Good luck; success; (countable) An instance of unexpected good luck; a stroke of luck; also, a lucky characteristic. 

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