blotch vs watermark

blotch

noun
  • Blotting paper. 

  • An irregularly shaped area. 

  • An uneven patch of color or discoloration. 

  • A bright or dark spot on old film caused by dirt and loss of the gelatin covering the film, due to age and poor film quality. 

  • A dark spot on the skin; a pustule. 

  • Any of various crop diseases that cause the plant to form spots. 

  • Imperfection; blemish on one’s reputation, stain. 

verb
  • To develop blotches, to become blotchy. 

  • To mark with blotches. 

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 blotch and watermark occurred in a corpus of books? (source: Google Ngram Viewer )