1853, "infected with pox," from pox + -y (2). As a deprecatory adjective, attested in English dialects by 1899.
Entries linking to poxy
pox n.
"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.
-y 2
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy). Adjectives such as hugy, vasty are artificial words that exist for the sake of poetical metrics.