hotfoot vs on the fly

hotfoot

adv
  • Hastily; without delay. 

adj
  • Moving with haste or zeal. 

verb
  • To run (a distance). 

noun
  • The prank of secretly inserting a match between the sole and upper of a victim's shoe and then lighting it. 

on the fly

adv
  • Spontaneously or extemporaneously; done as one goes, or during another activity. 

  • While in the air, without having touched the ground. 

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