Word History: “Oh yes, Mater, we had a posh time of it down there.” So in Punch for September 25, 1918, do we find the first recorded instance posh, meaning “smart and fashionable.” A popular theory holds that it is derived from the initials of “Port Out, Starboard Home,” the cooler, and thus more expensive, side of ships traveling between England and India in the mid-19th century. The acronym POSH was supposedly stamped on the tickets of first-class passengers traveling on that side of ships owned by the Peninsular and Oriental Steam Navigation Company. No known evidence supports this theory, however. Another word posh was 19th- and early 20th-century British slang for “money,” specifically “a halfpenny, cash of small value.” This word is borrowed from the Romany word påšh, “half,” which was used in combinations such as påšhera, “halfpenny.” Posh, also meaning “a dandy,” is recorded in two dictionaries of slang, published in 1890 and 1902, although this particular posh may be still another word. This word or these words are, however, much more likely to be the source of posh than “Port Out, Starboard Home,” although the latter source certainly has caught the public’s etymological fancy.

The story goes that the more well-to-do passengers travelling to and from India used to have POSH written against their bookings, standing for ‘Port Out, Starboard Home’ (indicating the more desirable cabins, on the shady side of the ship). Unfortunately, this story did not make its appearance until the 1930s, when the term had been in use for some twenty years, and the word does not appear to have been recorded in the form ‘P.O.S.H.’, which would be expected if it had originated as an abbreviation. Despite exhaustive enquiries by the late Mr George Chowdharay-Best, researcher for the OED, including interviews with former travellers and inspection of shipping company documents, no supporting evidence has been found.

According to lore, the term originates with British vessels crossing the Atlantic. The ventilation systems worked with large intakes that would gather air as the ship moved and allow it to flow down into the rooms though ducts. The sea winds would sometimes blow the smog produced by the steam engines into the intakes, which lead to unpleasantly smoky air inside the rooms.

For a premium, travelers could select rooms on the side of the ship that was less likely to have smoke blown into the intakes. This was dependent on which direction the ship was traveling–I believe it was the port (left) side when traveling west and the starboard when traveling east. Round-trip travelers who had paid for this convenience had an acronym printed on their ticket, indicating “Port Outbound; Starboard Return” or “P.O.S.H”. The term gradually became used to refer to the wealthy people who could afford this.

Other sources claim this as myth, and that the term originates from British slang for money. The OED first cites the term in 1890, meaning “a dandy”, and there’s is compellingly little hard evidence to support the ticket acronym. Nonetheless I think it’s a clever story.

It means smart and fashionable like a dandy. I have added some references for you do read. Sorry. Not meant to be a history lesson.

[Origin: 1915–20; of obscure orig.; cf.posha dandy (recorded as British slang in 1890); the popular notion that the word is an acronym from port out(ward), starboard home, said to be the preferred accommodation on ships traveling between England and India, is without foundation]

Another word posh was 19th- and early 20th-century British slang for “money,” specifically “a halfpenny, cash of small value.” This word is borrowed from the Romany word påšh, “half,” which was used in combinations such as påšhera, “halfpenny.”

slang adj. very smart, luxurious

This word is sometimes said to have been derived from the initials, “port out, starboard home,” referring to the more expensive side for accommodations on ships formerly traveling between Europe and India. This suggestion lacks foundation. The origin of the word is uncertain

an addition to the excellent answers re Port Out Starboard Home…I believe it also related to the “awnings”

on the ship and how the position of the sun on departure and return would effect the temperature of the cabins.