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chicken shit

Idioms  
  1. Contemptibly petty or insignificant. For example, He has spent his life making up chicken shit rules that nobody follows anyway . This expression gained currency during World War II, when it was often applied to the enforcement of petty and disagreeable military regulations. [ Vulgar slang ; c. 1930]

  2. Cowardly, as in You're not too chicken shit to come along, are you? [ Vulgar slang ; mid-1940s]