abstruseness vs rebus

abstruseness

noun
  • The property of being abstruse; abstrusity. 

rebus

noun
  • An arrangement of pictures, symbols, and/or words representing phrases or words, especially as a word puzzle. 

  • An arrangement of pictures on a coat of arms which suggests the name of the person to whom it belongs. 

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