fetter vs throw a spanner in the works

fetter

verb
  • To restrain or impede; to hamper. 

  • To shackle or bind up with fetters. 

noun
  • A chain or similar object used to bind a person or animal – often by its legs (usually in plural). 

  • Anything that restricts or restrains. 

throw a spanner in the works

verb
  • To introduce a problem, dilemma or obstacle, something unexpected or troublesome. 

How often have the words fetter and throw a spanner in the works occurred in a corpus of books? (source: Google Ngram Viewer )