Port and Starboard

Port and Starboard refer to the left and right sides of a vessel, respectively, from the perspective of someone facing the front (bow) of the vessel.

Whilst used in China from the 4th century A.D., the fixed sternpost rudder was not seen in Europe until the late 12th, early 13th centuries. Before that a large broad oar, a “steer board”, was lashed, or otherwise fastened, to the right-hand side of the ship (because the average steersman was right handed), and the right side has come down to us as “starboard”.

Likewise, so as not to damage the "steer board", vessels always came into port - alongside the wharf, jetty or embankment - on the other or left-hand side of the vessel. Until the early 19th century this side of the vessel was commonly called the "larboard" side, (possibly deriving from its use as the "loading side"). The change to "port" (made official in the Royal Navy in 1844, however there are records of "port" being used, possibly because a vessel's loading port was on that side) was made to stop any confusion caused by the similar sounds of "starboard" and "larboard". It is not known why it took so many centuries to make such an obviously practical and potentially life-saving change.

Reference: "The Oxford Companion to Ships and the Sea."