Answer:
In government, Popular will refers to a certain action or condition that is actively desired by the majority of the people. In a democratic country, every actions made by the government should be based on the popular will. If the people don't think that the government is doing a good enough job to actualize it, they could easily replace that position with another person.
Constitution is a set of fundamental principles that is used as a basis for the future laws to be created. In United States, constitution is considered as a "higher law". Meaning that if any of the future legislations violate any part of the constitution, those legislations should not be passed.
It is impossible for future government to pass legislations that satisfy the will of the people if the core foundation of the higher law itself is violating that popular will. Because of this, Constitution should be written as per the wheel and aspiration of people .