set on foot vs unleash

set on foot

verb
  • To originate; to put into action. 

unleash

verb
  • To precipitate; to bring about. 

  • To free from a leash, or as from a leash. 

  • To let go; to release. 

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