muddy the waters vs nonplus

muddy the waters

verb
  • To make something unclear and difficult to understand. 

nonplus

verb
  • To bewilder or perplex (someone); to confound, to flummox. 

noun
  • A state of bewilderment or perplexity. 

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