blind alley vs blunder

blind alley

noun
  • Used other than figuratively or idiomatically: see blind, alley. A street or passageway that leads nowhere. 

  • A course of inquiry that leads nowhere. 

blunder

noun
  • A clumsy or embarrassing mistake. 

  • A very bad move, usually caused by some tactical oversight. 

verb
  • To make a clumsy or stupid mistake. 

  • To do or treat in a blundering manner; to confuse. 

  • To move blindly or clumsily. 

  • To cause to make a mistake. 

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