pitter-patter vs tiptoe

pitter-patter

noun
  • A soft, percussive sound, as of tiny feet, or of rain on a rooftop. 

tiptoe

noun
  • The tip of the toe. 

verb
  • To walk quietly with only the tips of the toes touching the ground. 

adj
  • Standing elevated, on or as if on the tips of one's toes. 

  • Moving carefully, quietly, warily or stealthily, on or as if on the tips of one's toes. 

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