Explain the significance of the child's name?

The name “Pearl” evokes a biblical allegorical device—the “pearl of great price” that is salvation.

Pearl is exactly what the name means. She is Hester's treasure. There is a sense of irony in that the town feels that Pearl is an unholy bastard child who shows signs of oddness and perhaps darker themes. Pearl is, in fact, a free spirit who brings a sense of innocence and light to this dark community. Pearl is a result of two people who are actually in love. She is the one thing in Hester's life that shines and keeps Hester reason to withstand the abuse inflicted upon her.