headwater vs mouth

headwater

noun
  • The source (and the initial part) of a stream 

mouth

noun
  • The end of a river out of which water flows into a sea or other large body of water. 

  • The opening of a creature through which food is ingested. 

  • The crosspiece of a bridle bit, which enters the mouth of an animal. 

  • An outlet, aperture or orifice. 

  • A loud or overly talkative person. 

verb
  • To form or cleanse with the mouth; to lick, as a bear licks her cub. 

  • To take into the mouth; to seize or grind with the mouth or teeth; to chew; to devour. 

  • To form a mouth or opening in. 

  • To carry in the mouth. 

  • To pick up or handle with the lips or mouth, but not chew or swallow. 

  • The prompter mouthed the words to the actor, who had forgotten them. 

  • To form with the mouth. 

  • To utter with a voice that is overly loud or swelling. 

  • To speak; to utter. 

  • To examine the teeth of. 

  • To make the actions of speech, without producing sound. 

  • To exit at a mouth (such as a river mouth) 

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