expression vs poker face

expression

noun
  • The action of expressing thoughts, ideas, feelings, etc. 

  • A specific blend of whisky. 

  • A colloquialism or idiom. 

  • An arrangement of symbols denoting values, operations performed on them, and grouping symbols. 

  • The process of translating a gene into a protein. 

  • A facial appearance usually associated with an emotion. 

  • (manufacturing) The act of pressing or squeezing out. 

  • A particular way of phrasing an idea. 

  • A piece of code in a high-level language that returns a value. 

  • The tone of voice or sound in music. 

  • emotional involvement or engagement in a text read aloud rendered by the voice of the reciter or the reader 

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 expression and poker face occurred in a corpus of books? (source: Google Ngram Viewer )