backset vs pratfall

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. 

pratfall

noun
  • A humiliating mistake. 

  • A fall onto the buttocks. 

  • A staged trip or fall, often for comedic purposes. 

verb
  • To fall on to the buttocks. 

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