thigh vs trouser leg

thigh

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

  • 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. 

trouser leg

noun
  • Either of the legs of a pair of trousers 

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