flail vs tremble

flail

verb
  • To wave or swing vigorously 

  • To beat using a flail or similar implement. 

  • To thresh. 

  • To move like a flail. 

noun
  • A weapon which has the (usually spherical) striking part attached to the handle with a flexible joint such as a chain. 

  • A tool used for threshing, consisting of a long handle with a shorter stick attached with a short piece of chain, thong or similar material. 

tremble

verb
  • To shake, quiver, or vibrate. 

  • To fear; to be afraid. 

noun
  • A shake, quiver, or vibration. 

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