backslide vs hark-back

backslide

noun
  • A backward regression; a reverting back to a worse state. 

  • A dance move in which the feet are alternately slid back and the heels lifted, giving the illusion of walking forwards while actually moving backwards. 

verb
  • To revert back into a life of sin after being saved. 

  • To regress; to slip backwards or revert to a previous, worse state. 

  • To shirk responsibility; to renege on one's obligations or commitments. 

hark-back

noun
  • 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). 

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

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