A short for Mary.
It derives from Malle and Molle, which were both also diminutive forms of the name.
Other forms of the name are: Maria, Mollie, Polly, Pollie, Maia, Miren, Mari, Miriam, Marianne, Mariette, Manon, Marica, Maja.
Famous bearers are: Molly Ringwald, Molly Quinn, Molly Parker, Molly Bee, Molly Shannon, Molly Brown.
Molly is a popular name in Sweden, Northern Ireland, Ireland and Scotland.