port

Port, meaning the left side of a ship when facing forward, became standard nautical terminology in the mid-nineteenth century, replacing the older term 'larboard.' The change was practical: 'larboard' and 'starboard' sounded too similar, especially when shouted across a deck in a storm. The confusion could be fatal. The Royal Navy officially adopted 'port' in 1844. The U.S. Navy followed in 1846.

The word 'port' in this context comes from the fact that ships traditionally docked with their left side facing the port (harbor). The steering oar was on the right side (starboard, from stēorbord), so the left side was the side that could be placed against a dock without damaging the steering mechanism. The loading port — the opening in the hull through which cargo was loaded — was also on the left side. Left became port because the port was on the left.

The mnemonic 'port is left' — or 'port wine is red, and port's navigation light is red' — has been taught to sailors for over a century. The red light on the port side and the green light on the starboard side prevent collisions at night. An approaching ship's light colors tell you which side of the ship you are seeing and, therefore, which direction it is heading.

The earlier word 'larboard' came from Middle English ladebord (loading side), from lade (to load). The side where cargo was loaded. The etymology was sensible. The phonetics were dangerous. A captain shouting 'hard to larboard!' in a gale could be heard as 'hard to starboard!' The simpler, shorter, more distinct 'port' solved the problem.