birthday suit vs mannequin

birthday suit

noun
  • Nakedness, unclothed skin; an exposure of a human's natural anatomy without clothing. 

  • Used other than figuratively or idiomatically: see birthday, suit. 

mannequin

noun
  • A dummy, or life-size model of the human body, used for the fitting or displaying of clothes. 

  • A jointed model of the human body used by artists, especially to demonstrate the arrangement of drapery. 

  • An anatomical model of the human body for use in teaching of e.g. CPR. 

How often have the words birthday suit and mannequin occurred in a corpus of books? (source: Google Ngram Viewer )