Al Muhsi

Iḥṣāʾ is counting with nothing left over; the root’s old sense is counting out with pebbles, ḥaṣā, one stone laid down for one thing. It is arithmetic done with the hands, by somebody who cannot afford to lose track.

The written form is not in the Qur’an — the name is carried by the list — though the verb is there, in an ayah about a record that leaves out nothing small and nothing large. Nothing is lost in an accounting like that. That includes the parts nobody else counted, and the parts you long ago stopped counting yourself.