regret vs rue

regret

verb
  • To feel sorry about (a thing that has or has not happened), afterthink: to wish that a thing had not happened, that something else had happened instead. 

  • To feel sorry about (any thing). 

noun
  • Emotional pain on account of something done or experienced in the past, with a wish that it had been different; a looking back with dissatisfaction or with longing. 

  • The amount of avoidable loss that results from choosing the wrong action. 

rue

verb
  • To repent of or regret (some past action or event); to wish that a past action or event had not taken place. 

noun
  • Any of various perennial shrubs of the genus Ruta, especially the herb Ruta graveolens (common rue), formerly used in medicines. 

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