prattle vs talk the hind leg off a donkey

prattle

verb
  • To speak incessantly and in an inconsequential or childish manner; to babble. 

noun
  • Silly, childish talk; babble. 

talk the hind leg off a donkey

verb
  • To talk a lot. 

How often have the words prattle and talk the hind leg off a donkey occurred in a corpus of books? (source: Google Ngram Viewer )