patter vs rat-a-tat

patter

verb
  • To speak glibly and rapidly, as does an auctioneer or a sports commentator. 

  • To spatter; to sprinkle. 

  • To make irregularly repeated sounds of low-to-moderate magnitude and lower-than-average pitch. 

noun
  • A soft repeated sound, as of rain falling, or feet walking on a hard surface. 

  • One who pats. 

  • Glib and rapid speech, such as from an auctioneer or a sports commentator. 

rat-a-tat

How often have the words patter and rat-a-tat occurred in a corpus of books? (source: Google Ngram Viewer )