backset vs plummet

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. 

plummet

noun
  • A decline; a fall; a drop. 

  • A violent or dramatic fall. 

verb
  • To drop swiftly, in a direct manner; to fall quickly. 

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