Sling your Hook (Origin)
What Is the Origin of the Saying "Sling your Hook"?The term sling your hook is polite way of telling someone to go away. This term has a nautical origin. Hook was a name given to the ship's anchor, and the sling was the cradle that housed the anchor. Therefore, to sling your hook meant to lift anchor, stow it and sail away.
A Competing TheoryAt least as late as the 1930s, dockers in the Port of London used handheld cargo hooks to pull the loads from ships onto their backs. When a ship arrived for unloading, the dockers congregated on the dock side looking for work, and a foreman would select the men he wanted. Those who weren't selected were told to "sling yer 'ook!" (i.e., put their hooks away and leave).
(Thanks to Keith Kennedy for this entry.)