flounder vs knock on wood

flounder

verb
  • To act clumsily or confused; to struggle or be flustered. 

  • To flop around as a fish out of water. 

  • To be in serious difficulty. 

  • He gave a good speech, but floundered when audience members asked questions he could not answer well. 

  • To make clumsy attempts to move or regain one's balance. 

noun
  • A bootmaker's tool for crimping boot fronts. 

  • A European species of flatfish having dull brown colouring with reddish-brown blotches; fluke, European flounder, Platichthys flesus. 

  • Any of various flatfish of the family Pleuronectidae or Bothidae. 

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 flounder and knock on wood occurred in a corpus of books? (source: Google Ngram Viewer )