mottle vs speckle

mottle

verb
  • To mark with blotches of different color, or shades of color, as if stained; to spot; to maculate. 

noun
  • A distinguishing blotch of color. 

  • A mottled coloration or pattern. 

speckle

verb
  • To mark with speckles. 

noun
  • A small spot or speck on the skin, plumage or foliage. 

  • Kind; sort. 

  • A cluster of interchromatin granules in a nucleus. 

  • The random distribution of light when it is scattered by a rough surface. 

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