c.1300 (implied in pertly), "evident, unconcealed," shortened form of Middle English apert "open, frank," from Old French apert, from Latin apertus, past participle of aperire "to open" (see overt). Sense of "saucy, bold" first recorded late 14c. Less pejorative meaning "lively, brisk, in good spirits" (c.1500) survives in U.S. dialectal peart (with Middle English alternative spelling). Related: Pertness.