"Show (or shake) a Leg" (now) meaning "to get out of bed"

Supposedly shouted at sailors in their hammocks either (by some sources) to prove they were awake, or (by others) to prove that the lump still in the hammock was female and was still entitled to be sleeping off the night's exertions before she was bundled back ashore with the other prostitutes. And, no, there was not enough room to try standing up. HMS Victory in Portsmouth (UK) is an excellent visit to see what conditions were like in the good old days.

Rod Ward