lower jaw vs yap

lower jaw

noun
  • The part of the face below the mouth; the jaw. 

  • Specifically, the bone therein; the mandible of humans and other vertebrates that, with the cranium, composes the skull. 

yap

noun
  • The mouth, which produces speech. 

  • The high-pitched bark of a small dog, or similar. 

  • Casual talk; chatter. 

  • A badly behaved child; a brat. 

verb
  • Of a small dog, to bark. 

  • To talk, especially excessively; to chatter. 

  • To rob or steal from (someone). 

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