Question

Why port and starboard instead of left and right?

Answer 1

Steorbord, lit. "side on which a vessel was steered," from steor- "rudder, steering paddle" + bord "ship's side." Cf. O.N. stjornborði, Low Ger. stürbord, Ger. Steuerbord. Early Germanic peoples' boats were propelled and steered by a paddle on the right side. Fr. tribord (O.Fr. estribord), It. stribordo are Gmc. loan-words.  

port 

Meaning "left side of a ship" is attested from 1543, from notion of "the side facing the harbor" (when a ship is docked). It replaced larboard in common usage to avoid confusion with starboard (q.v.); officially so by Admiralty order of 1844 and U.S. Navy Department notice of 1846. Fig. sense "place of refuge" is attested from 1426; phrase any port in a storm first recorded 1749.