Medieval rhyming diminutive of Molly (from Mary), following the pattern Mary → Molly → Polly.
Polly has one of the more puzzling etymological journeys in the English naming tradition. It began as a medieval nickname for Mary — a name of Hebrew origin meaning "beloved" or "sea of bitterness" — via the intermediate form Molly. The shift from Mary to Molly to Polly reflects a common medieval English naming practice called rhyming variation, in which nicknames were generated by changing the initial consonant of an existing diminutive.
Thus Margaret became Maggie became Peggy, and Mary became Molly became Polly — a linguistic game of telephone that somehow produced an entirely new name. Polly has been woven into English folk culture for centuries. "Polly Put the Kettle On" dates to at least the eighteenth century, embedding the name in domestic English life.
"Pretty Polly" became a term of endearment and later a brand name. John Gay's 1728 *The Beggar's Opera* features Polly Peachum as its spirited heroine, one of the great comic-romantic roles in English theatrical history. Polly also became the canonical name for a talking parrot — a usage so entrenched it passed into the language as almost proverbial — giving the name an association with clever, imitative speech and cheerful companionship.
The name reached peak popularity in the United States in the early twentieth century and declined through the mid-century, but has experienced a gentle, sustained revival since the 2010s as part of a broader enthusiasm for vintage English names that feel charming without feeling fusty. Names like Nell, Hattie, Dot, and Polly — the nicknames of Victorian and Edwardian England — carry an appealing combination of historical character and unpretentious warmth. Polly in particular benefits from its bright double-L ending and its associations with wit and good humor rather than solemnity.