dilute vs hark back

dilute

noun
  • An animal having a lighter-coloured coat than is usual. 

adj
  • Of an animal: having a lighter-coloured coat than is usual. 

  • Having a low concentration. 

  • Weak; reduced in strength by dilution; diluted. 

verb
  • To cause the value of individual shares or the stake of a shareholder to decrease by increasing the total number of shares. 

  • To become attenuated, thin, or weak. 

  • To weaken, especially by adding a foreign substance. 

  • To make thinner by adding solvent to a solution, especially by adding water. 

hark back

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). 

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

  • To call back (hounds); to recall. 

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

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