Posted by Deejay on December 30, 1999
The origin of shake a leg as I have been lead to understand was derived from an old navy saying to "show a leg". When ships would put in port they would restrict the crew to the ship to avoid desertions, and they would allow the married sailors to have their wives join them aboard ship. When it came time for the ship to set sail, the call would be made in the bunk area to show a leg from underneath the covers and allow the females to dress and leave the ship. This was during the 1700 and 1800's. The phrase has apparently been twisted from "show a leg" into "shake a leg".
See the meaning and origin of 'shake a leg'.