dilemma vs mystery

dilemma

noun
  • A circumstance in which a choice must be made between two or more alternatives that seem equally undesirable. 

  • A difficult circumstance or problem. 

  • A type of syllogism of the form "if A is true then B is true; if C is true then D is true; either A or C is true; therefore either B or D is true". 

  • Offering to an opponent a choice between two (equally unfavorable) alternatives. 

mystery

noun
  • Something secret or unexplainable; an unknown. 

  • Someone or something with an obscure or puzzling nature. 

  • A religious truth not understandable by the application of human reason alone (without divine aid). 

  • A particular event or series of events in the life of Christ. 

  • A sacrament. 

  • A secret religious celebration, admission to which was usually through initiation. 

  • A craft, art or trade; specifically a guild of craftsmen. 

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