step on vs subdue

step on

verb
  • Used other than figuratively or idiomatically: see step, on. 

  • to adulterate a drug for the purpose of increasing its bulk, and therefore its profit; to dilute, cut. 

subdue

verb
  • To overcome, quieten, or bring under control. 

  • To bring (a country) under control by force. 

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