goad vs radical stimulus

goad

verb
  • To encourage or stimulate. 

  • To incite or provoke. 

  • To prod with a goad. 

noun
  • That which goads or incites; a stimulus. 

  • A long, pointed stick used to prod animals. 

radical stimulus

How often have the words goad and radical stimulus occurred in a corpus of books? (source: Google Ngram Viewer )