POSH
In my Grandmothers' days a POSH was the notso automatic washing machine. The Tub was barrel shaped but made of corrugated galvanised steel and called a poshing tub though no doubt it was designed to replace (and look like) a wooden barrel. The agitator was called a dolly posh or posher and looked loke a milking stool with a spade handle coming out of the seat. Motive force was provided by woman power and invariably involved a vertical and a helical motion. Unless you were really POSH and sent it all to a laundary or really really POSH and had a woman "who does".
The Port Out and Starboard Home theory is disputed by many accedemics.