G-string vs undershorts

G-string

noun
  • On a stringed musical instrument, the string that produces the note of G. 

  • A type of loincloth or breechcloth. 

  • A scanty covering for the genitalia, with a thin strip of fabric that passes between the buttocks. 

undershorts

How often have the words G-string and undershorts occurred in a corpus of books? (source: Google Ngram Viewer )