When I was singing on steamboats on the Mississippi River, I learned that the word POSH came from the fact that the prevailing winds on an ocean voyage took the cinders flying out of the stacks and deposited the soot on the passengers sitting on the starboard side (right side) when the boat was outward bound. The port side (left side) was relatively clean. When the ship was Homeward bound, the port side was dirty and the starboard side was clean.

That made "P"ort "O"ut and "S"tarboard Home, or P.O.S.H. -- the preferred place to be when crossing the ocean.

For what it's worth.

Art Thieme