There is no meaning to it, just an ancient Tamil name, passed down over the generations. Must have been the name of a great King.
It is shortened to Niro and is commonly mistaken for the Roman Emperor Nero or for the Hollywood actor Robert De Niro. The shortened version is well liked by people and thought to sound pretty cool.

Dude who went to Dr. Norman Bethune for one year and then left.

Name of a person. Tamil language... no meaning