drip vs knock on wood

drip

verb
  • To whine or complain consistently; to grumble. 

  • To have a superabundance of valuable things. 

  • To rain lightly. 

  • To be wet, to be soaked. 

  • To fall one drop at a time. 

  • To leak slowly. 

  • To let fall in drops. 

noun
  • A limp, ineffectual, or uninteresting person. 

  • Style; swagger; fashionable and/or expensive clothing. 

  • A drop of a liquid. 

  • A falling or letting fall in drops; act of dripping. 

  • A dividend reinvestment program; a type of financial investing. 

  • An apparatus that slowly releases a liquid, especially one that intravenously releases drugs into a patient's bloodstream. 

  • That part of a cornice, sill course, or other horizontal member, which projects beyond the rest, and has a section designed to throw off rainwater. 

knock on wood

verb
  • To take a customary action to ward off some misfortune that is believed to be attracted by a presumptuous statement. 

intj
  • Hopefully; a self-directive to undertake the customary action to ward off bad luck. 

How often have the words drip and knock on wood occurred in a corpus of books? (source: Google Ngram Viewer )