Shake a leg is an idiom which means to hurry up, to get going. Shake a leg is usually used as an imperative, which is a form of grammar that is a command or request. The first use of shake a leg to mean hurry up is found in the New York Magazine in 1904. The origins of the phrase shake a leg are murky, though there are claims that the term comes from the American Civil War, when after a battle, stretcher-bearers would violently jostle a leg or arm to see if they could elicit a response from a victim on the field and thereby ascertain if he were alive or dead.
The second of meaning of shake a leg is to dance, presumably having evolved from the terms shake a heel or shake a foot, which were popular terms meaning to dance in the 1660s.
Otherwise, rest assured, it would have been like any other date night; he would’ve been in that driver’s seat honking for me to “shake a leg” or we were going to miss the first showing of “Planet of the Apes” at the Moonlite Drive In. (Sunday Dispatch)
CFPB Should Shake a Leg on Payday Loan Rules (American Banker)
Liven up! Shake a leg! For gosh sakes. (The Washington Post)
Actor Upen Patel, who will shake a leg with his girlfriend Karishma Tanna in the upcoming dance based reality show ‘Nach Baliye 7’, says it’s a great chance for him to “emote romance”. (The Indian Express)
“We do a lot of dance music, and I hope people will want to get up and shake a leg.” (The Winston-Salem Journal)