ASH-SHAHEED-The All and Ever Witnessing The All Observing Witness

The One Who is ever observing everything and everyone He created. The One Who witnesses the seen and the unseen, all actions and even thoughts and intentions and He is the ultimate Witness on the Day of Judgement. The One who nothing is absent from Him.
Allah, Exalted be He, says, “Allah is sufficient as a witness.” (Surat An-Nisaa’, 4:79)
This name means the One who is aware of everything and the One from whom nothing is hidden. He will be a witness, on the Day of Judgement, to what we have done due to His absolute knowledge of everything. None of our secrets is hidden from Him.

Benefits of belief in this name include the following:

Fearing Allah and trying our best to say and do only those things that are pleasing to Him.
Taking care not to oppress people or encroach on their rights.
Demonstrating sincerity and observing piety in words and deeds.
Being assured that our rights will be secured, for Allah is a witness; His testimony is the weightiest testimony, and the witness He bears regarding someone will prevail and He will certainly be sufficient for him.

The One who directly and ever-presently observes everything in creation. The One from whose knowledge nothing is hidden.

The One who witnesses both that which is seen and that which is unseen. The One who has knowledge of all that happens everywhere at all times.

The One who is the ultimate witness on judgment day.

From the root sh-h-d which has the following classical Arabic connotations:

to bear witness
to offer testimony
to have knowledge of, to experience
to be present with

This name is used in the Qur’ān. For example, see 85:9