I would like to inquire about the meaning of the name Marwan, and the ruling on naming a newborn with it?

Al-Marw refers to white, gleaming stones. Al-Marwah was named so because its stones are white and gleaming. The addition of "alif" and "nun" in "Marwan" is for emphasis and to indicate the perfection of the attribute. There is no objection to naming a newborn with this name.