strengthener vs underpinning

strengthener

noun
  • One who, or that which, gives or adds strength. 

underpinning

noun
  • A basis for something. 

  • The lower body or legs. 

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

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