accrual vs amassment

accrual

noun
  • An increase; something that accumulates, especially an amount of money that periodically accumulates for a specific purpose 

  • from the creditor's viewpoint, a charge incurred in one accounting period that has not been, but is to be, paid by the end of it. 

amassment

noun
  • That which is amassed; a large quantity (of something). 

  • The act of amassing. 

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