stiffener vs underpinning

stiffener

noun
  • Anything added to something in order to stiffen it, such as a support beam, or starch for a collar. 

  • An alcoholic drink taken to fortify oneself. 

underpinning

noun
  • A support or foundation, especially as a structure of masonry that supports a wall. 

  • The lower body or legs. 

  • A basis for something. 

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