contrivance vs smokescreen

contrivance

noun
  • Something overly artful or artificial. 

  • A means, such as an elaborate plan or strategy, to accomplish a certain objective. 

  • A (mechanical) device to perform a certain task. 

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 contrivance and smokescreen occurred in a corpus of books? (source: Google Ngram Viewer )