al-Qādir

The One who possesses the power and the ability to measure-out anything and everything.

The One who has the capability to make any decree and to determine what will be.

The One whose decree determines the measure and distribution of all things.

The One who does as He wills, acting or not acting in accord with whatever He decides.

From the root q-d-r which has the following classical Arabic connotations:

to measure something
to make manifest the measure of something
to distribute or apportion (as though by measure), measure-out
to decree, to ordain, to decide a matter (as though measuring it to fit)
to exercise thought in preparing something, to make use of reason (measuring out)
to have the power to accomplish, to be rendered able, capable
to be able to prevail, to be empowered, to have control over

This name is used in the Qur'ān. For example, see 77:23, 6:37

Muqtadir is an intensive form of the root q-d-r which emphasizes the Supreme Power to enforce or enact whatever Divine wisdom decides; being omnipotent, having the ability to do everything.

Qādir is a less intensive form of the root q-d-r which describes the attribute of being able to decree, ordain, appoint, measure-out, decide.

These both involve power in the sense of power being the intention by which something comes into being according to a certain measure and a certain willful decree, as in saying 'kun' (Be!), and it is.

Related names:

Qawī - the One who is all-mighty and possesses inexhaustible strength.

Matīn - the One whose nature it is to be firm, determined, steadfast.

Qādir - the One whose nature it is to decree, ordain, appoint, measure-out, decide.

Muqtadir - the One whose supreme power enforces whatever Divine wisdom decrees or decides; omnipotent, able to do everything.