hind leg vs underpinning

hind leg

noun
  • Either of the two legs towards the rear of a four-legged animal. 

underpinning

noun
  • The lower body or legs. 

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

  • A basis for something. 

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