masking vs shadow mask

masking

noun
  • An entertainment at which the guests conceal their faces with masks. 

  • The practice of wearing safety masks, such as face masks. 

  • The act by which something is masked; the act of masking, of concealing or disguising. 

shadow mask

noun
  • A plate punched with tiny holes that separate the coloured phosphors in the layer behind the front glass of the screen. Three electron guns at the back of the screen sweep across the mask, with the beams only reaching the screen if they pass through the holes. 

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