Name takes serious significance to those involved in magic like magicians or devils.
If one reaches a certain level of power, it is even possible to curse and dominate the soul at the very moment he gets to know the other party’s name.
The contract with devil uses this principle and the contract made with the name is impossible to break whatever happens.
「On my name, Lirshana, I swear.
To lend you my power in accordance with the contract」