quelling vs sapping

quelling

noun
  • The act by which something is quelled. 

adj
  • causing something to quell or be quelled 

sapping

noun
  • The act by which something is sapped or depleted. 

  • The act of excavating trenches. 

  • The act of being struck with a sap or club. 

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