plip vs tremble

plip

noun
  • A light sound or action like liquid hitting a surface. 

verb
  • To make the sound of liquid hitting a hard surface. 

  • To lock or unlock using a remote control locking device. 

tremble

noun
  • A shake, quiver, or vibration. 

verb
  • To shake, quiver, or vibrate. 

  • To fear; to be afraid. 

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