The One who is perfect, whole, prosperous and content.

The One who is the source of all peace, wholeness and safety.

The One who has rendered all of creation to be perfect, whole, prosperous and content.

The One whose creation is free of imperfections, free of faults and free of error. 

From the root s-l-m which has the following classical Arabic connotations:

to be peaceful, quiet, tranquil, content, friendly, reconciled
to be free from imperfections, free from faults, complete, whole, sound
to be safe, secure, well, healthy, prosperous

This name is used in the Qur’ān. For example, see 59:23

This ancient Semitic root of s-l-m implies every manner of wholeness, completeness and prosperity.

Many seek peace by struggling, battling and trying to impose their will on others, yet external peace will only prevail as a reflection of inner peace. The only path to outer peace is awareness of the tranquil depths of  inner peace, and the only source of such inner peace is the One known as as-Salām.

According to Rāghib the word Islam, which arises form this same s-l-m root,  means to enter into salm… which means to enter into peace, or to enter into wholeness. That is, the word Islam means to be at peace with orreconciled with the ways and decrees of Allāh, and is often described as self-resignation, surrender or submission to the will of Allāh.