Since the entity receives a huge increase in strength in the form of a name, the brand is essential so as to prevent the receiver from hurting the person who named it.
After all, if the person who named it dies, the brand marking the entity also dissipates but not the name. To put it bluntly, the Naming process marks the entity with a brand of the bestower to control its actions that might be harmful to the bestower.
One needs immaculate control of the mana within them to name others. Also one cannot name an entity many times stronger than it. The reason behind Irene thinking of this method was because of the loyalty and bond displayed by the warhorse towards Simon.
