cool one's heels vs frequent

cool one's heels

verb
  • To wait, especially impatiently or restlessly. 

frequent

verb
  • To visit often. 

adj
  • Done or occurring often; common. 

  • Occurring at short intervals. 

  • Addicted to any course of conduct; inclined to indulge in any practice; habitual; persistent. 

How often have the words cool one's heels and frequent occurred in a corpus of books? (source: Google Ngram Viewer )