susurrus vs tremble

susurrus

noun

  • A whispering or rustling sound; a murmur. 

tremble

noun

  • A shake, quiver, or vibration. 

verb

  • To shake, quiver, or vibrate. 

  • To fear; to be afraid. 

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