at work vs on the hop

at work

prep
  • At play, in action. 

  • Used other than figuratively or idiomatically: see at, work. At one's workplace. 

  • Working, in the process of doing work. 

on the hop

prep
  • Playing truant from school. 

  • Spontaneous; unplanned. 

  • Unprepared; unready and unable to deal with something. 

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