mouthing vs utterance

mouthing

noun
  • Ranting; passionate speech devoid of meaning. 

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

utterance

noun
  • A manner of speaking. 

  • Something spoken. 

  • The ability to speak. 

  • An act of uttering. 

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