belt-tightening vs sapping

belt-tightening

noun
  • A reduction in expenditure, often as a result of financial restrictions. 

adj
  • Causing or involving a reduction in expenditure. 

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 belt-tightening and sapping occurred in a corpus of books? (source: Google Ngram Viewer )