on the run vs rushed off one's feet

on the run

prep
  • At a disadvantage; forced to abandon a position. 

  • Constantly traveling or moving from place to place. 

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

  • Fleeing. 

rushed off one's feet

adj
  • Extremely busy. 

How often have the words on the run and rushed off one's feet occurred in a corpus of books? (source: Google Ngram Viewer )