Nimaz was a Romulan Rite of Transition which is also known as the Naming.
It is a ceremony performed within a week of a child's birth where names are chosen after prominent Romulan citizens which can either be a hero, revered ancestor or some other person who has had a great impact within the Romulan Star Empire. It is a small private ceremony that affirms a newborn's purpose within the Star Empire which ensures that the child is well aware of their future obligations.
The choice of a name is carefully decided and the child is taught very early about the footsteps they are expected to follow. (Last Unicorn RPG module: The Way of D'era: The Romulan Star Empire)