In the Middle Ages, upper-class Britons and other European nobility in castles or large manor houses dined in the great hall. This was a large multi-function room capable of seating the bulk of the population of the house. The family would sit at the head table on a raised dais, with the rest of the population arrayed in order of diminishing rank away from them. Tables in the great hall would tend to be long trestle tables with benches. The sheer number of people in a Great Hall meant it would probably have had a busy, bustling atmosphere. Suggestions that it would also have been quite smelly and smoky are probably, by the standards of the time, unfounded. These rooms had large chimneys and high ceilings and there would have been a free flow of air through the numerous door and window openings.
It is true that the owners of such properties began to develop a taste for more intimate gatherings in smaller 'parlers' or 'privee parlers' off the main hall but this is thought to be due as much to political and social changes as to the greater comfort afforded by such rooms. Over time, the nobility took more of their meals in the parlour, and the parlour became, functionally, a dining room (or was split into two separate rooms). It also migrated farther from the Great Hall, often accessed via grand ceremonial staircases from the dais in the Great Hall. Eventually dining in the Great Hall became something that was done primarily on special occasions.
Towards the beginning of the 18th century, a pattern emerged where the ladies of the house would withdraw after dinner from the dining room to the drawing room. The gentlemen would remain in the dining room having drinks. The dining room tended to take on a more masculine tenor as a result.
In the 1930s and 40s, dining rooms continued to be separate from kitchens even as servant's rooms became less common in middle-class houses. In the 1950s and 60s, dining and kitchen areas were merged, and living rooms were merged with the kitchen-dining rooms.
During the COVID-19 pandemic, dining rooms that still existed were used as home offices or classrooms and were valuable for their seclusion.