It’s probably a chute for an old coal or wood heater. These are pretty common in houses built in the late 19th and early 20th century in the US.

I don’t remember how old I was when I figured it out, but I do remember being upset about being lied to about it. I’ve got 2 kids now, and whenever they would ask about Santa or the Tooth Fairy or anything like that, I would kind of turn the question around and ask how they thought it worked. Sometimes, I miss believing in that sort of magic, and I didn’t want to take that from them or lie to them, so that’s the balance I found. It seems to be working well. Our oldest had it pretty well figured out by around age 9…our youngest is almost 9 now, and she hasn’t straight up told me she knows it’s not real, but the kinds of questions she asks and how she reasons through her answers I think she’s figured it out mostly as well.

Thank goodness none of them were CEOs!