pretext vs smokescreen

pretext

noun
  • A false, contrived, or assumed purpose or reason; a pretense. 

verb
  • To employ a pretext, which involves using a false or contrived purpose for soliciting the gain of something else. 

smokescreen

noun
  • Anything used metaphorically to conceal or distract. 

  • Smoke used as a disguise, mask or cover, as of troops in battle. 

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