groin vs nether regions

groin

verb
  • To grunt; to growl; to snarl; to murmur. 

  • To build with groins. 

  • To deliver a blow to the genitals of. 

  • To hollow out; to excavate. 

noun
  • The surface formed by two such vaults. 

  • The crease or depression of the human body at the junction of the trunk and the thigh, together with the surrounding region. 

  • The genitals. 

  • The projecting solid angle formed by the meeting of two vaults 

  • The area adjoining this fold or depression. 

nether regions

How often have the words groin and nether regions occurred in a corpus of books? (source: Google Ngram Viewer )