pass oneself off as vs purport

pass oneself off as

verb
  • To pretend to be. 

purport

verb
  • To convey, imply, or profess (often falsely or inaccurately). 

  • To intend. 

noun
  • import, intention or purpose 

How often have the words pass oneself off as and purport occurred in a corpus of books? (source: Google Ngram Viewer )