Polly = Mary
First off, we have another case of the letter R being replaced by two L's. Then, the natural evolution of language turned Mary into Molly. And yes, more rhyming occurred, turning Molly into Polly.
Polly is a given name, most often feminine, which originated as a variant of Molly (a diminutive of Mary).
My Mary Ann born 1863 was called Pol and Polly. I think these days a lot of the old shortenings and nicknames have been forgotten because many of them are now used as names in their own right. Derek becomes Del, Terrence or Terry, Tel. Mary became Mol or Molly and that was frequently changed to Pol or Polly.
Nicknames: Mae, Maisy, Mamie, May, Mamie, Mimi, Minnie, Mitzi, Molly, Polly, Ray. Variations: Maartje, Mair, Máire, Maja, Mara, Maren, Mari, Maria, María, Marie, Marja, Marya, Maryam, Miriam. Namesakes: Mary-Kate Olsen, Mary Shelley.
Molly (also spelled Molli or Mollie) is a diminutive of the feminine name Mary.
The Church recognizes six “formal” titles for her, which corresponds to Church teaching and dogmas concerning her: Blessed Virgin Mary, Mother of God, Our Lady, Queen of Heaven, Immaculate Conception and Assumption.
Polly is a feminine name of Latin origin that means "star of the sea." Once used as an endearing pet name for "Molly" and "Mary," Polly has since matured into a timeless name in its own right.
Peggy from Margaret
Over the years, Maggie morphed into Meggie and Meg, likely because of accents changing the vowel sound. That continued to transform into the Peggy and Peg we know today, based simply on a trend of creating nicknames that rhyme. It's the same reason we have Bill from William.
Peggy is a feminine name of Greek and English origins. Traditionally used as a nickname for Margaret, it has since become a fun, adorable name in its own right. It translates to “pearl,” which is sure to remind baby that they're a dazzling, valuable addition to your family.
But many nicknames are traditionally used to replace a more formal name. For example, Molly may replace Margaret, Tom traditionally replaces Thomas, Polly for Mary, and Bill is commonly used for William.
William to Bill
Either way, the first written evidence of a William being called Bill was in the late 17th century when Irishmen mocked King William III of England by calling the hated Protestant conqueror "King Billy."
Originally a nickname of the feminine names Dolores and Dorothy, Dolly has become a given name in its own right. It is charmingly retro while evoking such legendary women as singer-songwriter Dolly Parton and First Lady Dolly Madison.
Polly was born and raised in the North of England, which is where she says the bulk of her accent hails from. “But I left when I was very young so maybe there's a touch of London in there,” she theorizes, saying she is “covering a lot of England” with her current accent.
Molly originated as a diminutive of Mary, spawning from medieval variations Malle and Molle. Molly has been used as a stand-alone pet form of Mary since the Middle Ages, and has been consistently popular as an independent name in the U.S. over the past several decades.
Slang: Sometimes Disparaging and Offensive. a term used to refer to or address a gay man (sometimes used facetiously).
The name Jack is a derivative of John, which originated in medieval England. The name went from John to Johnkin to Jankin to Jackin to, you guessed it, Jack. There is also a theory that Jack is Celtic in origin, meaning "healthy, strong, and full of vital energy."
The flower name comes from the Old English word dægeseage, meaning "day's eye". The name Daisy is therefore ultimately derived from this source. Daisy is also a nickname for Margaret because Marguerite, the French version of the latter name, is also a French name for the oxeye daisy.
Midge is a name primarily given to girls. This retro-chic title is a popular nickname for Margaret, which stems from the Greek word margarítēs, meaning “pearl.” Midge is also the name applied to many small biting insects throughout the UK and Ireland.
Sally is an English language feminine given name. The name originated as a pet name for the Hebrew name Sarah, but has since become used independently. It is also a nickname for Salome and Salimeh, which are especially popular in the Eurasian country Georgia.
Why is Eddard Stark called 'Ned'? Eddard is basically the Westerosi version of Edward. Ned is a nickname for Edward in the real world, allegedly through this process: “Mine Edward” → “Mine Ed” → “My Ned” → “Ned.”
The name of this character is stated to be short for Holiday (rather than a reference to the plant).
Maryam. This Urdu form of Miryam has the same meaning as the popular biblical name Mary; “drop of the sea,” “wished for child,” or “beloved.”
Muire (English: Mary) is an Irish name given exclusively to the Blessed Virgin Mary. The Irish name Máire is typically used for the name Mary. Muire is used exclusively for the Virgin Mary.
Gender: Mary is traditionally a feminine name. Marion, Marius, or Mario may be used as masculine equivalents.