“Pox began as 'pocks' — the plural of pock, a pustule — and lost its c in casual speech. The word for plague-spots is the oldest English medical term still in common use.”
Middle English pokkes was the plural of pokke — a pustule, a raised blister on the skin. The word comes from Old English pocc, a bag or pouch, describing the shape of the blister. By the 15th century, pokkes had contracted in speech to pox — the c dropped in the way English frequently drops consonants from clusters: 'and' became 'an,' 'ould' became 'ol' in 'could.'
The Great Pox — syphilis — arrived in Europe from the Americas with Columbus's returning sailors in 1493 or was already present and newly virulent. The term 'pox' was immediately applied to it: it produced pustules. By the late 15th century, a pox could mean smallpox, syphilis, or any pustular disease. The lack of specificity was a medical problem; physicians distinguished with qualifiers: the 'great pox' for syphilis, the 'small pox' for smallpox.
Chickenpox is the youngest of the pox-named diseases — the name appears in the 1680s. Why chicken? Various theories: the spots resemble chickpea seeds; the disease is mild compared to the great pox; the Old English gican (to itch) may have given it the 'chick' part. The chickenpox etymology remains unclear, though the disease is well-understood.
Edward Jenner's smallpox vaccine in 1796 — derived from cowpox — gave the word 'vaccine' from the Latin vacca, cow. Smallpox was declared eradicated by the WHO in 1980. The word pox, stripped of its most terrible referent, now mainly appears in 'chickenpox' and in the Shakespearean oath 'a pox on both your houses' — Mercutio's dying curse in Romeo and Juliet.
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Pox is almost the only remaining medieval medical term still in everyday English. The language of 15th-century illness — ague, dropsy, the flux, the falling sickness — has been replaced by Latin-Greek medical terminology. But pox survived, embedded in chickenpox and in Shakespeare's oath.
The disease that gave the word its worst associations — smallpox — has been eradicated. The word outlived the thing. Pox is now an orphaned term, retaining its force in metaphor and in one mild childhood disease, a ghost of the pustular catastrophes that once named it.
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