"Starboard" is a dialectic transliteration of "steerboard". The steer board preceded the rudder for steering boats, and was located on the right hand side of the vessel. It dates from before the Vikings.
"Port" is so called because the port was off the left hand side of the vessel when leaving harbour and heading north, when on the east coast of Britain, or heading south from the west coast, in both instances to take advantage of favourable ocean currents.
How it would have worked in the southern hemisphere is anyone's guess - port and sherry, maybe?
