"disease characterized by eruptive sores," late 15c., spelling alteration of pockes (late 13c. in this sense), plural of pocke "pustule" (see pock (n.)). Especially (after c. 1500) of syphilis.
Entries linking to pox
pock n.
"pustule raised on the surface of the body in an eruptive disease," Middle English pok, from Old English pocc "pustule, blister, ulcer," from Proto-Germanic *puh(h)- "to swell up, blow up" (source also of Middle Dutch pocke, Dutch pok, East Frisian pok, Low German poche, dialectal German Pfoche), from PIE root *beu- "to swell, to blow" (see bull (n.2)).
French pocque is from Germanic. The plural form, Middle English pokkes "disease characterized by pustules" (late 14c.) is the source of pox.
chicken pox n.
c. 1730, from chicken (n.) + pox. Perhaps so called for its mildness compared to smallpox [Barnhart], or its generally appearing in children, or its resemblance to chick-peas.