asseveration vs mouthing

asseveration

noun
  • An earnest affirmation; a declaration of support. 

mouthing

noun
  • Ranting; passionate speech devoid of meaning. 

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

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