Everything about "pox leber" as a minced oath, and an earlier source.

[JoJo_Jost]

poxplwt = poxplivr??  could be a phonetic spelling of blîver / blîven (“to remain”). As far as I know, the p and b are sometimes interchanged in handwriting. then it would come out as something like pox blîver.

“May smallpox remain (with you)” – in other words, “smallpox upon you” or “lasting smallpox.”

But I'm not sure!