"neat, trim, smart," hence "pert, jaunty," 1820, from perk (v.) + -y (2). Used of young women's breasts at least since 1937. Related: Perkily; perkiness. The earlier adjective was perk (1570s).
Entries linking to perky
perk v.
late 14c., perken, "to make oneself trim or smart," perhaps literally "to perch on a tree," from Old North French perquer "to perch" (Modern French percher; see perch (n.1), and compare perk (n.1)), on notion of a bird preening its plumage. Sense of "raise briskly, hold up smartly" is attested from 1520s; perk up "recover liveliness" is from 1650s. Related: Perked; perking.
Þe popeiayes perken and pruynen for proude On peren and pynappel.
["Susannah," Scottish alliterative poem, c. 1390]
-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.