pin-up vs sex on legs

pin-up

noun
  • A photograph, printed in a magazine or other publication, of a sexually attractive person (often nude or provocatively dressed), and intended to be removed and pinned up on a wall. 

  • The person so depicted. 

  • Figurehead, person who represents an idea, cause etc. 

sex on legs

noun
  • A person or persons considered to be very sexually attractive. 

How often have the words pin-up and sex on legs occurred in a corpus of books? (source: Google Ngram Viewer )