A pox is a disease that leaves the skin marked with spots. Chickenpox, smallpox, the pox.
Smallpox was named small to distinguish it from the great pox, which was syphilis, and it is the only human disease ever eradicated — declared gone in 1980. Chickenpox is the common childhood one. A pox on you is an old curse wishing the disease on somebody, kept alive almost entirely by historical drama. Note that pox is the old plural of pock, so the singular mark is a pockmark.
1nounpoxA disease that leaves the skin marked with spots.
“Smallpox killed about three in ten of those it infected.”
pox is a spotted disease.
Pox is the plural of Middle English pocke, a pustule, respelt as it sounded. The curse sense came from wishing a literal pox on somebody, and pox came to mean a curse in itself.
Middle English
pocke
English, today
pox
From the plural of Middle English pocke. See also pock. The curse sense involves metonymy: wishing a literal pox upon someone is the original form of pox-relevant curse, and the word pox itself also came to mean curse.
Etymology from Wiktionary, CC BY-SA