muddiness vs opacity

muddiness

noun
  • The characteristic of being muddy. 

opacity

noun
  • The state or quality of being opaque, not allowing light to pass through 

  • The state or quality of being inaccessible to understanding. 

  • A measure of relative impenetrability to electromagnetic radiation such as light. 

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