fair crack of the whip

Australian colonial term meaning to give someone a fair chance or cut them a break.

Probably derived from when the original convict Australians were whipped with a "cat o nine tail" for any old indiscretion whether deserved or not...

Woman: Get out of my bed!
Man: Why?
Woman: Because you are not performing to my expectations softy!
Man: Fair crack of the whip! I'm drunk! ....Mumble mumble... Crazy Sheila.....