backset vs difficulty

backset

noun
  • A check; a relapse; a discouragement; a setback. 

  • Whatever is thrown back in its course, such as water. 

verb
  • To plow again in the fall; said of prairie land broken up in the spring. 

difficulty

noun
  • An objection. 

  • Physical danger from the environment, especially with risk of drowning 

  • An obstacle that hinders achievement of a goal. 

  • The state of being difficult, or hard to do. 

  • An awkward situation or quarrel. 

  • That which cannot be easily understood or believed. 

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