Etymology
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larboard (n.)

"left-hand side of a ship" (to a person on board and facing the bow), 1580s, alteration of Middle English ladde-borde (c. 1300), perhaps literally "the loading side," if this was the side on which goods were loaded onto a ship, from laden "to load" (see lade) + bord "ship's side" (see board (n.2)).

Altered 16c. by influence of starboard, then, to avoid confusion of similar-sounding words, it was largely replaced by the specialized sense of port (n.4). The Old English term for it was bæcbord, literally "back board" (see starboard), a term which remains in the other Germanic tongues.

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port (n.4)

"the left side of a ship" (looking forward from the stern),  1540s, probably from the notion of "the side facing the harbor" (when a ship is docked); thus from port (n.1). On old-style vessels the steering oar was on the right side, thus they would tie up at a wharf on the other side. It replaced larboard in common usage to avoid confusion with starboard; officially so by Admiralty order of 1844 and U.S. Navy Department notice of 1846. As an adjective by 1857.

U. S. Navy Department, Washington, Feb. 18, 1846.
It having been repeatedly represented to the Department that confusion arises from the use of the words "larboard" and "starboard"' in consequence of their similarity of sound, the word "port" is hereafter to be substituted for "larboard." George Bancroft, Sec. of the Navy.
The whalemen are the only class of seamen who have not adopted the term port instead of larboard, except in working ship. The larboard boat was this boat to their great-grandfathers, and it is so with the present generation. More especially is this the case in the Atlantic and South Pacific fleets; but recently the term port-boat has come into use in the Arctic fleet. [Fisheries of U.S., V. ii. 243, 1887]
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