down payment vs due date

down payment

noun
  • A payment representing a fraction of the price of something being purchased, made to secure the right to continue making payments towards that purchase. 

  • Any initial commitment signifying an intention to carry out a larger future commitment, even though no legal rights or obligations are secured. 

due date

noun
  • The date of payment in financial arrangements. 

  • The date on which a pregnant woman is expected to give birth. 

  • The date by which a book (or other item) borrowed from a library must be returned. 

  • The date by which a task is supposed to be completed. 

How often have the words down payment and due date occurred in a corpus of books? (source: Google Ngram Viewer )