ball and chain vs difficulty

ball and chain

noun
  • One's wife, as a symbol of restraint. 

  • A heavy iron ball attached to a prisoner's leg by a chain as a means of restraint. 

  • Anything that restricts one's freedom or opportunities. 

difficulty

noun
  • An objection. 

  • Physical danger from the environment, especially with risk of drowning 

  • An obstacle that hinders achievement of a goal. 

  • The state of being difficult, or hard to do. 

  • An awkward situation or quarrel. 

  • That which cannot be easily understood or believed. 

How often have the words ball and chain and difficulty occurred in a corpus of books? (source: Google Ngram Viewer )