triclinium
A couch for reclining at mealtimes, extending round three sides of a table, and usually in three parts.
Seated on the triclinium in the midst is a middle-aged man, with a high and noble brow; the fine aquiline nose, so patrician, as if their eagle had set his own seal on his warlike race;...
A dining room furnished with such a triple couch.
The manor house seemed still as the night itself. Morgan la Blanche had taken herself to a couch in the triclinium, choosing it rather than one of the cubicles leading from the atrium.
Where it comes from
Borrowed from Latin trīclīnium, from Ancient Greek τρικλίνιον (triklínion).
Adapted from the Wiktionary entry triclinium (CC BY-SA 4.0).