Treasure is often carried on ships, and so are guns.

Ever wondered where the phrase "son of a gun" comes from? It turns out that during the Age of Sail when ships were in port and sailors went out to fraternize with the ladies, often the only privacy they could find was on the gun deck back aboard their ship.

If and when these ladies later found themselves with child, they would often apply to the Royal Navy for assistance for their newborn children conceived on ship. For liability reasons, naval records relating to these children often did not include the name of their father. Rather, instead of the father's name was listed the number of the gun to which the father was assigned, in order to help guard the father's identity.

Subsequently, sons of these sailors became known as "a son of a gun."