curtail vs lessen

curtail

verb
  • To shorten or abridge the duration of something; to truncate. 

  • To limit or restrict, keep in check. 

noun
  • A scroll termination, as of a step, etc. 

lessen

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

  • To become less. 

conj
  • unless. 

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