I advise anyone who thinks
posh might stand for 'Port Outward Starboard Home' to go to
http://www.wordorigins.org/ and click on 'Posh' in the alphabetical index. That's a very full discussion of the subject and I've got nothing to add to it, except to say that I doubt if it would make much difference to the temperature of your cabin whether it was on the port side or the starboard side.