ambiguity vs obscurity

ambiguity

noun
  • The state of being ambiguous. 

  • words or statements that are open to more than one interpretation, explanation or meaning, especially if that meaning cannot be determined from its context. 

obscurity

noun
  • The state of being unknown; a thing that is unknown. 

  • The quality of being difficult to understand; a thing that is difficult to understand. 

  • Darkness; the absence of light. 

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