“Goody Two-Shoes” is the name given to a poor orphan - Margery Meanwell.
She is so poor as to possess only one shoe and is so delighted when given a pair of shoes by a rich gentleman that she keeps repeating that she has “two shoes”.
She ran out to Mrs. Smith as soon as they were put on, and stroking down her ragged Apron thus, cried out, “Two shoes, Mame, see two shoes”.
And so she behaved to all the people she met, and by that means obtained the name of “Goody Two-Shoes”.
By virtue of hard work, she makes good and marries a wealthy widower - thus mimicking the Cinderella theme of virtue being finally rewarded.