ground-plan vs underpinning

ground-plan

noun
  • Framework or pattern. 

  • A diagram showing set layout. 

  • Floorplan. 

  • Hypothetical ancestor of a clade. 

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 ground-plan and underpinning occurred in a corpus of books? (source: Google Ngram Viewer )