mussitate vs yackety-yak

mussitate

verb

  • To talk indistinctly; to mutter. 

  • To say (words, etc.) indistinctly; to mutter. 

yackety-yak

verb

  • To talk pointlessly and uninterruptedly. 

noun

  • prolonged chatter; uninterrupted, idle talk; gossip 

How often have the words mussitate and yackety-yak occurred in a corpus of books? (source: Google Ngram Viewer )