quell vs step on

quell

verb
  • To subdue, put down, or silence (someone or something); to force (someone) to submit. 

  • To die. 

  • To suppress, to put an end to (something); to extinguish. 

noun
  • A subduing. 

  • An emotion or sensation which rises suddenly. 

  • A source, especially a spring. 

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. 

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