Q: A friend and I have a wager going. He says you should never say "right" or "left" on a boat but always "port" and "starboard." I think there are times when you can say "left." In fact, I think that I've heard it used on Navy ships. Who's right...err, correct?
A: You win, but your friend has a point. The origin of "starboard" goes back to the days when ships had a steering oar, or "steer board," instead of a rudder. The other side of the boat was "laboard," probably a corruption of "lee board," a device to prevent sailing ships from sliding sideways in the wind. The word "port" was substituted for larboard quite recently. The claim is that ships laid their laboard sides to the quay when in port to protect their fragile steer boards.

Until the 20th century, sailors gave helm orders that referenced the tiller, not the direction of the turn. Thus, a left turn called for starboard helm. The tiller went to the starboard, causing the rudder to swing to port and the bow to pivot to port. This is why in James Cameron's 1997 movie Titanic, the officer yells, "hard a-starboard," but the quartermaster turns the wheel to the left.

During World War I, a lot of farm boys were pressed into naval service. Rural lads assigned to steering battleships became confused by turning to their left for a starboard helm command. To sort out the chaos, the British navy issued a regulation requiring that all steering directions be given in "left" or "right" based on the quartermaster's point of view. The U.S. Navy and merchant ships followed suit.

For several decades, U.S. ships were required to have signs in their wheelhouses identifying the left side of the ship from the right. It's still required that steering instructions be given in "left"  or "right." However, the port side is still the port side for every other purpose.