What is symbolic about the name "Pearl"?

Hester probably considers Pearl beautiful and rare, just like real pearls. Puritans also considered pearls as a luxury and vanity. Hester and Dimsdale sinned when they had an affair, and Pearl is the result of that luxury and vanity.

Pearl are created by an irritant entering an oyster, usually a piece of sand or grit. Hester was the irritant thrust into the oyster that was the Puritan society. She "spoke out" via her affair with Dimsdale. The result is Pearl.