Allright is ah kinda trick.
Ah was talking to a Canadian Helo Pilot over some beers of course ! and the talk about POSH came up , this is how he explained the origin.
Before air transport the British would use luxury steamers to go to India (which was the jewel of the empire ) apparently because of the direction of travel and the rotation of earth , the choice seats leaving England were on the port side and the best seats coming back from India were on the starboard side.
So the rich and famous would by seats or cabins Port Outbound.. Starboard Home