Definition of "Molly"

"My name's Molly. It is an old-fashioned name, and I was christened Mary. But Papa likes Molly.""That's right. Keep to the good old fashions, dear.""Well, I must say I think Mary is prettier than Molly, and quite as old a name, too," said Mrs Hamley."I think it was," said Molly, lowering her voice, and dropping her eyes, "because mamma was Mary, and I was called Molly when she lived."

1864 August – 1866 January, [Elizabeth] Gaskell, chapter 6, in Wives and Daughters. An Every-day Story. […], volumes (please specify |volume=I or II), London: Smith, Elder and Co., […], published 1866

But Mother and Father and Grandpa and Grandma and Uncle and Aunty couldn't very well call out "Millicent Margaret Amanda" every time they wanted her, so they shortened it to "Milly-Molly-Mandy" which is quite easy to say.

1928, Joyce Lankester Brisley, chapter 1, in Milly-Molly-Mandy Stories