According to legend the word posh is derived from a phrase printed the on tickets of P&O passengers during the days of the Raj – ‘Port Out Starboard Home’. Berths on the portside in the northern hemisphere were mostly shaded on the journey out and on the starboard side on the way in. Therefore the most expensive berths were deemed POSH. There is no evidence to confirm this. What is more it would actually have made little, if any, difference to the cabin temperature.
