countenance vs poker face

countenance

noun
  • Calm facial expression, composure, self-control. 

  • Appearance, especially the features and expression of the face. 

  • Favour; support; encouragement. 

verb
  • To tolerate, support, sanction, patronise or approve of something. 

poker face

noun
  • 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. 

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

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