In the old Scandinavian languages (and in Swedish today) Starboard was (is) called Styrbord.
'Styr' = 'steer' in english
'bord' means the side of the ship. For example; to board a ship meant that you used hooks and stuff to attach your own ship to the ship you where attacking, The hooks griped in holes and the plankings. 'A bord' also means one of the plankings that the whole boat consisted of.
It originates from the ships that the Vikings [850 - 1050 A.C.] used. The stern was "pointy" so the rudder had to be put on one side, hence 'styrbord'. The other side is called 'Babord' which meant that the first mate had his back to it. That side is called 'port' in english because that is the side that went up against the shore or jetty.