This phrase is used to describe someone who is unstable, unpredictable, or uncontrollable. This term has its roots in Naval warfare in the Age of Sail. Due to their weight the cannons on a sailing ship, which were generally referred to as guns, were secured to prevent them from moving about with the waves of the sea or to prevent damage from the enormous recoil when fired. A cannon that had become loose of its restraints and was rolling dangerously about the deck could cause immense damage to the vessel and crew.
The Great Storm, a force two hurricane with wind speeds of up to 95 miles per hour, hit the south of England and Wales on 26th November 1703, the strong winds finally abating on 28th November. The Church of England declared that the storm was God’s retribution for the sins of the nation and it couldn’t have hit at a worse time. That year saw the greatest concentration of both naval and merchant shipping on the British coast to that date. Due to 
William Kidd, better known as Captain Kidd, had a very unfortunate career. He is believed to have been born into a poor seaman’s family in Dundee, Scotland in around 1654, later settling in New York. Not much else is known about his early life except that he took to the seas like his father before him. Although active in the grey area of privateering, it is likely that he never intended to adopt a life of piracy and was simply a victim of circumstances.