advance payment vs prepayment

advance payment

noun
  • The part of a contractually due sum that is paid or received in advance for a good, service or social security payment. 

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 advance payment and prepayment occurred in a corpus of books? (source: Google Ngram Viewer )