defray vs pay off

defray

verb
  • To pay or discharge (a debt, expense etc.); to meet (the cost of something). 

pay off

verb
  • To pay back; to repay. 

  • To bribe, especially to deter oversight. 

  • To pay back (repay, pay off) the entirety of a loan, thereby effecting the release of a lien on. 

  • To fall to leeward, as the head of a vessel under sail. 

  • To become worthwhile; to produce a net benefit. 

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