E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
now called port (q.v.). (Starboard is from Anglo-Saxon steorabord, the steer-board, or right side of a ship.) Larboard is the French bâbord, the left-hand side of a ship looking towards the prow; Anglo-Saxon bc-bord.
She gave a heel, and then a lurch to port,
And going down head foremostsunk in short.
Byron: Don Juan (The Shipicreck).
To give a heel is to sway over on one side. Here it means a heel to the starboard side.