What is the origin of the phrase 'Rushing around like a headless chicken?'

The phrase means running around in a panic-stricken, disorderly manner.

It seems that it originated in England, when chickens were killed by chopping off their heads. Sometimes the headless body would run around for a while before dying.

http://www.phrases.org.uk/bulletin_board/38/messages/1397.html

There has been one documented case of 'Mike the headless chicken' who went on to live for 18 months after having its head cut off.

http://www.miketheheadlesschicken.org/

https://en.wikipedia.org/wiki/Mike_the_Headless_Chicken