Where did the term loose cannon derive?

Answer 1

From the 18th century British Navy. They began refitting their cannons aboard battleships to penetrate newer ironclad ships. To do this, the cannons used considerably more powder, and were much heavier, but on many of the ships, the support structures were not reinforced to accommodate the extra stress. As a result, many of these cannons became dislodged by the kickback and would often fly off the deck or roll around loose, causing damage and injury.

Answer 2

A cannon that breaks from its attachment to a ship, particularly a sailing ship

Answer 3

It means you might hurt someone without warning. Like firing a cannon not probably secured to something.