Nitin comes from the Sanskrit Root called as Nitya. Nitya means "order" or "regulatedness". In the Vishnu Sahasranaama (1000 Divine Names of Lord Vishnu) Nitya is one of the names of Vishnu.
Nitin means that which exists in the regulated order. The energy aspect of the Lord which is called his maya or sakthi is the one that exists in the Lord and his creation. So Nitin is the energy aspect of the Lord and it is popular among the Vaishnavites to keep this name. (Vaishnavism is not a trait that belongs to caste but to the mode of worship relating to Vishnu