inarticulate vs mumbling

inarticulate

adj
  • not articulated in normal words. 

  • unable to speak with any clarity 

  • speechless 

  • not having joints or other articulations 

noun
  • An animal belonging to the subphylum Inarticulata. 

mumbling

noun
  • An act in which someone mumbles something 

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