In the early days, refrigeration was a new and expensive thing. Even when the electric fridge was invented and built for the domestic consumer (right around the time this building was built -1916), the common way of keeping goods cold was by buying ice from the Iceman who would cometh on a regular basis to supplieth the ice for the ice box.
Beholdeth: Proof via Wikipedia (so you know it’s true):
< Exhibit A Exhibit B>
Now, it came to pass that some clever guy came up with a way to save money on ice. Maybe he didn’t like his iceman to cometh around so much. Maybe buying what is essentially just frozen water from the river, seemed silly to him. So, he (I’m guessing it was a he, it always was, back then) figured that, in the colder days at least, he could keep some of his food in a little box built into the exterior wall of the apartment. Because this box was built into the exterior wall, the cold from outside would penetrate the box easily, thus keeping his lovely perishables (like butter or something) nice and cool. Smart, huh? It’s also a good spot to keep your potatoes and what-have-yous because it’s a cool, dark spot!
Behold, we have such a thing in our kitchen! (lost the door thought)
And this how it looks with the door on… (This is NOT our kitchen. It’s just a photo of some other person’s dilemma, er, kitchen.)