Dinning room? What? Who even says that? Never in my life have I heard that. I have heard various delightful terms from 19th century hotels, ships and railways, for example, the Dining Salon in ships and hotels, and of course, on railrroads, the Dining Car (more commonly known as the Restaurant Car in Europe, but in the US, Pullman called their dining cars or “diners” Restaurant Cars, and often these had a crew of only one or two chef/waiters and a small menu and existed to provide a meal service for sleeping car passengers on trains that lacked a dining car on all segments (remember that Pullman operated “car lines” where their sleeping cars would be forwarded from one train to another, for example, my railroad historical society has a 1956 Pullman from the Union Pacific’s City of St. Louis, which was used to provide through service from the West Coast to Washington, DC, via St. Louis, bypassing Chicago for a faster connection; this was painted in UP colors so I have no idea who it was forwarded on to, perhaps the Chessie, but before the 1930s, for a few decades every nearly railroad* painted all of their cars in a dark olive green color known as “Pullman Green”, which created the elegant homogenous appearance of American “Heavyweight” stainless steel passenger trains in the Roaring Twenties, when the US passenger rail network was arguably both at its peak, and was also the world leader technologically speaking, with the heaviest, strongest rails of any railroad on the newly electrified Northeast Corridor, the largest number of steel cars for safety in the event of collisions, the largest percentage of automatic couplers (to this day, most European railways except for the broad gauge system of the former Soviet Union rely on manual link and pin couplers and buffers, requiring a trainman to stand between the buffers when coaches are coupled or uncoupled, and manually hook up the couplers, and also the electrical and air brake connections between the coaches, before climbing up and lowering the footplates between the cars; also in the Eastern US and Eastern Canada, most single level passenger trains have level boarding onto their platforms, which most European railways lack, meaning on most trains in Europe you have to step up to board the train or use other means if in a wheelchair; meanwhile out west the hi-level cars such as the Chicago commuter cars and Amtrak Superliners are nearly wheelchair accessible on their lower level, but at the cost of wheelchair-bound passengers not being able to move between carriages).
*except the Pennsylvania (which painted all their cars in a tuscany/burgundy sort of color, the Denver & Rio Grande Western which used yellow at least on their narrow gauge trains (I think the uP used yellow on some trains as well), and the Baltimore & Ohio which used a stately royal blue and white, and even had a train called the Royal Blue (Royal Blue and Gold were also the colors of Wagon Lits in Europe, which was Pullman’s European counterpart and business partner, whereas Mitropa, which took over the operations of Wagon Lits in Germany during the first world war, and DSG (Deutsche Schlaffwagen Gessellschaft, I think), which took over the operations of Mitropa in East Germany after WWII), used a red color not hugely different from that used on the Pennyslvania)