perjure vs string on

perjure

verb
  • To make a false oath to; to deceive by oaths and protestations. 

  • To cause to violate an oath or a vow; to cause to make oath knowingly to what is untrue; to make guilty of perjury; to forswear; to corrupt. 

  • To knowingly and willfully make a false statement of witness while in court. 

string on

verb
  • To continue to convince (someone) of something untrue; to maintain a lie or scam aimed at (someone). 

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