concord vs difficulty

concord

verb
  • To agree; to act together 

noun
  • Agreement of words with one another, in gender, number, person or case. 

  • A state of agreement; harmony; union. 

  • An agreeable combination of tones simultaneously heard; a consonant chord; consonance; harmony. 

  • A variety of sweet American grape, with large dark blue (almost black) grapes in compact clusters; a Concord grape. 

difficulty

noun
  • 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 objection. 

  • An awkward situation or quarrel. 

  • That which cannot be easily understood or believed. 

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