on the hop vs rushed off one's feet

on the hop

prep
  • Playing truant from school. 

  • Spontaneous; unplanned. 

  • Unprepared; unready and unable to deal with something. 

rushed off one's feet

adj
  • Extremely busy. 

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