meaning larboard or left side, is an abbreviation of porta il timone (carry the helm). Porting arms is carrying them on the left hand.
“To heel to port” is to lean on the left side (Saxon, hyldan, to incline). “To lurch to port” is to leap or roll over on the left side (Welsh, llercian).
“She gave a heel, and then a lurch to port,
And, going down head-foremost, sunk in short.”