accrue vs lessen

accrue

verb
  • To become an enforceable and permanent right. 

  • To increase, to rise 

  • To accumulate. 

  • To reach or come to by way of increase; to arise or spring up because of growth or result, especially as the produce of money lent. 

  • To be incurred as a result of the passage of time. 

lessen

verb
  • To make less; to diminish; to reduce. 

  • To become less. 

conj
  • unless. 

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