Why is ionisation Energy also known as ionisation Potential?

Explanation

The energy necessary to promote an electron from the ground state `(n_1 = 1)` to infinity `(n2 = prop)` from a free gaseous atom to form unipositive ion is known as ionisation energy.
`DeltaE=(2pi^2m.z^2c^4)/h^2 (1/h_1^2 - 1/n_2^2) [h_1 = 1, n^2 = prop]`
This lonisation energy is also known as ionisation Potential, because the former is measured by the potential through which an electron is accelerated.