hind leg vs thigh

hind leg

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

thigh

noun
  • That part of the leg of vertebrates (or sometimes other animals) which corresponds to the human thigh in position or function; the tibia of a horse, the tarsus of a bird; the third leg-section of an insect. 

  • The upper leg of a human, between the hip and the knee. 

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