I live in a village in southwestern Germany, and there are a lot of holloways in this area.
https://en.wikipedia.org/wiki/Sunken_laneIn elementary school we would sometimes have field trips and do little hikes.
At one of those hikes, my class, I was about 7 at the time, was going through one of the many holloways with older kids.
They told us a story where a group of encircled French soldiers would find their end in one of the holloways, and with their dying breath summon a monster.
There actually is a holloway called "Franzosenhohle" (Frenchmen-holloway) at the outskirts of the village, and in Napoleonic times and before that the French were sometimes invading this area as it is not to far away from the border. The story I've been told might be a childish spin on a story about an actual skirmish in the area, who knows.
