cool one's heels

(idiomatic) To wait, especially impatiently or restlessly.

Example: 1711, Jonathan Swift, The Journal to Stella (published 1766), ch. 4, letter 31:
  I cooled my heels in the cloisters till nine, then went in to the music-meeting.
1863, Joseph Sheridan Le Fanu, The House by the Church Yard, ch. 27:
  Remember I say it—he'll cool his heels in a prison, if he's no wiser than of late, before a twel'month.
1873, Mark Twain, The Gilded Age, ch. 28:
  Indeed his annoyance had time to augment a good deal; for he was allowed to cool his heels a full half hour in the ante-room before those gentlemen emerged and he was ushered into the presence.
1881, Robert Louis Stevenson, "Aes Triplex" in Essays of Robert Louis Stevenson:
  "Though Death has been cooling his heels at my door these three weeks, I have not had time to see him."
2001 June 24, Nancy Gibbs, "The Currie Riddle," Time:
  Once in the White House, Currie became an expert at making small talk with visiting dignitaries, members of Congress, Cabinet Secretaries and other Administration officials as they cooled their heels waiting for the ever tardy Clinton.