genital organ vs undercarriage

genital organ

noun
  • An organ used in sexual reproduction or sexual stimulation; a sex organ; (in plural) genitalia. 

undercarriage

noun
  • The genitalia. 

  • The supporting structural framework of a vehicle. 

  • The landing gear of an aircraft. 

How often have the words genital organ and undercarriage occurred in a corpus of books? (source: Google Ngram Viewer )