armorial bearing vs watermark

armorial bearing

noun
  • Heraldry that consists of a design or image depicted on a shield 

watermark

noun
  • A translucent design impressed on the surface of paper and visible when the paper is held to the light. 

  • A mark indicating the level to which water has risen. 

  • A logo superimposed on a digital image, a television broadcast, etc. 

  • A value stored in a datafile to ensure its integrity, so that if the file's contents are changed then the watermark will no longer match the contents. 

verb
  • To mark paper with a watermark. 

  • To mark a datafile with a digital watermark. 

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