an inner room: the private, enclosed chamber set deep inside a house or building, away from its public parts
This is the room you reach by going deep inside, shut off from the street and the public parts of a house. That inwardness is the whole point of the word. It is the space where a person sleeps, retreats, weeps, hides, or speaks with someone in private, the most secluded room in the building.
Because it names the innermost space, it naturally covers the bedroom (often spelled out in Hebrew as the "room of the bed"), the private quarters of a king or a bride, and the interior storerooms of a large building such as the temple, where valuables were kept out of public view.
Hebrew poetry then stretches the same word to any hidden inner depth. A gossip's words sink into the "chambers of the belly" (a person's inmost self); the path of the wicked leads down to the "chambers of death" (the far recesses of the grave); and God set the stars in the "chambers of the south" (the remote, unseen reaches of the sky).