AdrianH is vaguely on the right track. Placed vertically in a building, something goes through it, nothing to do with chimneys or wood burners, but it would have had something to do with warmth and security....
I'll let you have that woody v8. No dragons involved sadly. Well done.
Back in the good old days when you lived in the same house as your animals for the security of your animals against foxes, wild dogs etc and with the added warmth in winter you literally split the room in half using wood or slates, the hole is to allow the animals to pass their heads through to get to the troughs. Known locally as a be-boeuf.