Neighbours
Near the word, not the word
Each of these is defined by something else. Only fumoir is defined by atmosphere.
Nearby rooms
Den
Defined by privacy. Can be brightly lit and still a den.
Snug
Defined by size. A small room, not necessarily a dark one.
Lounge
Defined by function. If it echoes, this is what you have.
Speakeasy
Defined by concealment. The door does the work, not the light.
Not this
Dark academia
Books and tweed. A fumoir has no required reading.
Industrial
Exposed metal and hard surfaces. A fumoir absorbs; industrial reflects.
Mid-century
Light wood, clean legs, bright rooms. The opposite instinct.
Maximalism
Fumoir is dark, not busy. Few objects, all of them heavy.