I found another "poxleber"

[Rafal]

As I understood from this forum, “pox” was something like a very vulgar and peasant‑like swear word.

Not really. "Pox" is just a writing form of "bock" - he-goat.
It feels Bavarian/Tirol. These guys often replaced "b" with "p". Instead of writing "blut" (blood) they wrote "plut" etc.

The vulgarity comes from the fact that you often made oaths, charms etc. by calling body parts of Christ and saints like "corpus Christi" - body of Christ. See my thread: You are not allowed to view links. Register or Login to view.  Replacing in with goat could sound blasphemous.

See: You are not allowed to view links. Register or Login to view.