furtherance vs prepayment

furtherance

noun
  • Promotion. 

  • Advancement or progress. 

  • The act of furthering or helping forward 

prepayment

noun
  • A payment in advance. 

  • An asset recognized in respect an expense incurred in a period for which the benefit will be received in a future period. 

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