crossword vs mare's nest

crossword

noun
  • The grid of such a puzzle 

  • A word puzzle in which interlocking words are entered usually horizontally and vertically into a grid based on clues given for each word. 

mare's nest

noun
  • A confused or complicated situation; a muddle. 

  • A great discovery which turns out to be illusory; a hoax. 

How often have the words crossword and mare's nest occurred in a corpus of books? (source: Google Ngram Viewer )