harry vs keep on at

harry

verb
  • To make repeated attacks on an enemy. 

  • To plunder, pillage, assault. 

  • To harass, bother or distress with demands, threats, or criticism. 

  • To strip, lay waste, ravage. 

keep on at

How often have the words harry and keep on at occurred in a corpus of books? (source: Google Ngram Viewer )