befog vs obnubilate

befog

verb
  • To envelop in fog or smoke. 

  • To confuse, mystify (a person); to make less acute or perceptive, to cloud (a person’s faculties). 

  • To obscure, make less clear (a subject, issue, etc.). 

obnubilate

verb
  • To make cloudy. 

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