The room where Andrew was discovered murdered was the sitting room. This room was primarily used to receive company, conduct business, or for casual entertaining. As for the Living room, that was more a formal room used by the family to relax or entertain a function, etc. Couches were usually in the sitting room and sofas in the living room, but not necessarily a general rule. The word couch originated with the French, meaning to lay down or recline. (laying down).(

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The 'couch' was more or less a place to sit and take a load off your feet. The word was taken from 'crouch' to sit or recline. If you were visited by a neighbor or friend you would entertain them in the sitting room where everyone would recline. More of a temporary practice then a "get yourself comfortable and stay a while." Even a psychiatrist had a couch where you could "reline" a while.
Sofa speaks more to relaxing or formal entertaining. When you retired for the evening with a book, tea, and some cookies.....yea

COOKIES

you would most likely do it in the 'living room' and on the 'sofa".
Unless it was at my house in 1960.
There were plastic slip covers, clear plastic, like the kind that holds your bank passbook or passport, on the sofa and chairs. You were not allowed to even enter the room, to say nothing about actually sitting on the furniture. Such was poverty. You had something nice you did not use it for fear of wearing it out. Only special occasions and only for company. No kids allowed. Even later when I was done with school. Still not allowed to sit on the "sofa". And lacking a 'sitting room' one was relegated to the dinning or kitchen table.