strike gently vs thwack

strike gently

thwack

noun
  • The act of thwacking; a strike or blow, especially with a flat implement. 

  • A heavy slapping sound. 

verb
  • To hit with a flat implement. 

  • To beat. 

  • To fill to overflow. 

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