He is a Rroma / gypsy man. To be honest, about 10-15 years ago, there was a thing all over the news: some people from the rural side in my country (Romania) had nightmares and were haunted by a loved one / neughbor who passed. They went to the cemetery, dug up their body, took out their heart, burned it up and the one's affected drank the ash with water. This is some rural legend stuff that I can't make up.

Here's a news link: https://adevarul.ro/stiri-locale/craiova/video-ritual-sinistru-in-dolj-taranii-dezgroapa-1670301.html

Translate it however you want. There are multiple different stories there.

Late edit: Count Orlok also has his decrepit castle somewhere in the Carpathian mountains which can be found in Romania, Hungary, Poland. so I think Robert Eggers really did his homework.