fall off the wagon vs hark back

fall off the wagon

verb
  • To cease or fail at a regimen of self-improvement or reform; to lapse back into an old habit or addiction. 

hark back

verb
  • To return to where one has previously been; to retrace one's steps. 

  • To allude, return, or revert (to a subject previously mentioned, etc.); also, to evoke, or long or pine for (a past era or event). 

  • To call back (hounds); to recall. 

  • Of hounds: to retrace a course in order to pick up the lost scent of prey. 

noun
  • An act of hounds retracing a course in order to pick up the lost scent of prey. 

  • An act of alluding, returning, or reverting (to a subject previously mentioned, etc.); also, an act of evoking, or longing or pining for (a past era or event). 

How often have the words fall off the wagon and hark back occurred in a corpus of books? (source: Google Ngram Viewer )