matter-of-fact vs poker face

matter-of-fact

adj
  • lacking emotion or colour 

  • of, or relating to facts only; literal, realistic 

  • straightforward, blunt, frank; treating the situation as normal; not embarrassed, coy, or dramatic. 

poker face

noun
  • Any similar expression used to prevent giving away one's motives, feelings, or situation. 

  • An impassive facial expression cultivated to prevent other players from determining whether one's actions in the game are the result of a quality hand, or of bluffing. 

How often have the words matter-of-fact and poker face occurred in a corpus of books? (source: Google Ngram Viewer )