bird's nest vs vagina

bird's nest

noun
  • Any tangle of fibers resembling a typical nest of a bird. 

  • A structure built by a bird as a place to incubate eggs and rear young. 

  • Any of several plants having some resemblance to the typical nest of a bird, eg, wild carrot (Dauca carota) 

vagina

noun
  • A sheathlike structure, such as the leaf of a grass that surrounds a stem. 

  • The vulva, or the vulva and the vaginal passage collectively. 

  • A similar part in some invertebrates. 

  • The passage leading from the opening of the vulva to the cervix of the uterus for copulation and childbirth in female mammals. 

  • A coward; a weakling; a pussy. 

How often have the words bird's nest and vagina occurred in a corpus of books? (source: Google Ngram Viewer )