mouthing vs uttering

mouthing

noun
  • Ranting; passionate speech devoid of meaning. 

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

uttering

noun
  • An utterance; something spoken. 

  • The crime of knowingly presenting forged documentation. 

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