grin vs mouthing

grin

noun
  • A smile in which the lips are parted to reveal the teeth. 

verb
  • To grin as part of producing a particular facial expression, such as a smile or sneer. 

  • To express by grinning. 

  • To smile, parting the lips so as to show the teeth. 

mouthing

noun
  • The act of forming a shape with the mouth, especially as part of sign language. 

  • Ranting; passionate speech devoid of meaning. 

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