quail vs tremble

quail

verb
  • To lose heart or courage; to be daunted or fearful. 

  • Of courage, faith, etc.: to slacken, to give way. 

  • To waste away; to fade, to wither. 

noun
  • The meat from this bird eaten as food. 

  • Any of various small game birds of the genera Coturnix, Anurophasis or Perdicula in the Old World family Phasianidae or of the New World family Odontophoridae. 

tremble

verb
  • To fear; to be afraid. 

  • To shake, quiver, or vibrate. 

noun
  • A shake, quiver, or vibration. 

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