concealment vs emission

concealment

noun
  • The practice of keeping secrets. 

  • protection from observation or surveillance. 

  • The condition of being hidden or concealed. 

emission

noun
  • The act of emitting; the act of sending forth or putting into circulation. 

  • A show; a program. 

  • Something which is emitted or sent out; issue. 

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