rule with a rod of iron vs scourge

rule with a rod of iron

verb
  • To rule with stern severity. 

scourge

verb
  • To strike with a scourge; to flog. 

noun
  • A source of persistent trouble such as pestilence that causes pain and suffering or widespread destruction. 

  • A whip, often of leather and often multi-tailed. 

  • A means to inflict such pain or destruction. 

How often have the words rule with a rod of iron and scourge occurred in a corpus of books? (source: Google Ngram Viewer )