What does the word POSH mean? :

Before getting to the origin, the meaning. Dictionary definitions are abundant. These reflect the most popular
Elegant, Smart, Splendid, Fashionable, Money and Rich .
According to my 60 year old Oxford Dictionary, the word is from obscure origin, English and first use is given as 1918. Relatively new word in the greater order of Things.
They most popular origin of this word is based on things nautical, specifically passages from England to India. The best sought after and consequently most expensive berths were those facing away from the sun. Both India and England being in the Northern hemisphere this would mean cabins on the port side (left) would be coolest on the trip to India, and on the starboard side (right) on the return trip. So, if you had enough money you could book your passage accordingly.
So for the shipping line to define this type of booking the letters P.O.S.H would be entered onto the ticket. Meaning Port Out Starboard Home. With time the abbreviation became the acronym Posh.
Problem is that there is absolutely no evidence that this was the case. Experts have done extensive digging around, and no written proof can be found. Shipping lines have no record of this procedure ever being implemented. As this took place in the past 100 years or so, there should be someone or a document of sorts that could verify, but there is nothing, zilch, nada.
Officially this is not the origin. One could argue that if this was not official then it could have been in the spoken word only. Subjective decision that one.
Another version is that the word had its origin from the Romany (Gypsy) coin, Pash that became English slang for money in the late 18 and early 1900’s.
Another possible origin was from the English magazine Punch. A satirical account of a man called Posh, that had all the attributes as per definitions, and dating from the late 1800’s.
The most popular version is therefore not necessarily the correct one, but the Jury is still considering this one.