In the primitive days of navigation, the helmsman stood at the stern of the ship, controlling the vessel’s direction by hand with a rudder.
The rudder was on the right side and called a steer board, or as the Anglo-Saxons called it, a “starboard.”
The left side of the ship is called the “port” side, because with the steering mechanism on the right it was the only side that could be brought to rest against a harbor or port.