Probably an old dumbwaiter.

good thought, wish it was.
but the floors are solid with not a single sign of an opening. no sign of an opening on the second floor. the dining room wall solid and no sign of an opening. here is the dining room wall.

It was just a guess, but, to me, the floors (and some of the moulding) do not look original, so it's hard to say that it didn't used to be open or what it would've been. Is there a basement beneath? Where was the kitchen originally? I also don't know that what you're using as a dining room was the dining room then. These things are always so difficult.

Clock?

The dumbwaiter wouldn't need an opening in the second floor--the mechanism could be in the space above the open area. And, room uses change over the years, especially in a house as old as yours. Without any more info on the size or layout of the house, you could have had double parlors and the dining room was elsewhere, like across a hallway from the opening.

I love old house archeology - figuring out what once was. It wasn't until I started taking apart my house that I really figured out what had been done to it - removing old kitchen flooring and cabinets and removing layers of paint and wall paper you start to see where the doors once were, where the original pine cupboards had hung (long gone before my time). I even could see the outlines of where the old crank wall telephone had hung and where a five foot kitchen sink with the rounded back splash had hung - the original paint color on the wall was a beautiful rich green and then they put in sink etc. so that subsequent paint jobs (brown, tan, etc.) didnt cover the original wall color.

I keep thinking that it might have been the original chase for the first heating system installed in the house. I just imaging a hulking furnace in the basement with tentacles of ducts reaching through the entire house. sure would be nice to find blueprints of the orignal design. But Somerville, Ma has no real records of our house and im not sure what type of heating was available in the 1850s

that room has a built in china cabinate so its clear that it was the dining room. the other side of the floor has two rooms separated by parlor doors

anyone have any examples of a space like that turnend into storage for keys and whatnot?

I'm extraordinarily curious. I find it hard to believe that the angled wall in the dining room isn't original... because of the floor. Am I seeing things or are the floor boards cut and patterned to conform to the odd angles of the walls? Sure looks like it.
Got to admit, my first thought on the nook on the other side was also 'dumb waiter' that had been opened up somewhat/fiddled with. Very curious.
Hope you find out something. I'd love to know.
Ging

Is there a corresponding angle in the opposite corner of the room?
Symmetry has always been sought, and the resulting dead space in the hallway was deemed by somebody as too good to go to waste, but whatever purpose it was put to did not use the full pointy depth of that dead space, so it was truncated at a depth that was usable for whatever purpose (phone, altar, niche for umbrella stand). I think it's far too small (and does have that angled side) for D/W, which would have been situated to open into a dining room or servery/butler's p. anyway
Casey

Is the original chimney still in your home? Just thought maybe this could have been a removed chimney since it looks about the same size as what I have. My chimney sits at a 45 degree angle in relation to all the walls, so my kitchen, dining room and one of the parlors all had a tiny 45 degree angle wall where the chimney was plastered over.
{{gwi:1564836}}From House
{{!gwi}}From House

Wow, that is a real head-scratcher.

And I don't have a clue.

Please let us know if you figure it out.

And you might post at wavyglass.org. There's a bunch of old house smarties over there.

Rose

Sometimes, a pattern will emerge if you draw to-scale plans for each floor & compare them. It might be apparent what changed over the years that created that little nook.