convenience vs expediency

convenience

noun
  • The quality of being convenient. 

  • Any object that makes life more convenient; a helpful item. 

  • A convenient time. 

verb
  • To make convenient 

expediency

noun
  • The quality of being fit or suitable to effect some desired end or the purpose intended; suitability for particular circumstance or situation. 

  • An expedient. 

  • Pursuit of the course of action that brings the desired effect even if it is unjust or unprincipled. 

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