The first name VIṤVAM spoke of he who is the “Universal-All”. When the question is asked as to WHO is that who represents this Universal-All, the answer is Viṣṇu.
Derived from the root Viṥ, it refers to someone who is present everywhere and he who has entered/penetrated into everything:
Yasmat vistam idam sarva tasya saktya mahatmanah, tasmad evo’cyate Viṣnur dãtoh praveśanat
The Shakthi of that supreme personality VISHNU has entered into the VIṤVAM
Expressed as Veveṣti – he is the one who has enveloped everything there is, embraced as it were all that we see and know – limitless and unlimited by Desha (Space), Kala (Time) and Vastu (objects)
“Vevesti Vyapnoti iti Vishnu”
He who’s nature is all pervading and who envelops all, he is Vishnu”
Therefore the VIṤVAM is Viṣṇu.
“Antar-bahishca Tat Sarvam Vyapya Narayana Stitaha” (Narayana Suktam/Upanishad)
“Naryana stands pervading and interpenetrating the entire cosmos – both within and without.”
“I am Viṣṇu because I measured the sky and the earth (as Vamana) and as I have pervaded Universe and extend even beyond it” (Mahabharata)
As VIṤVAM he is the Universal-all and as Vishnu he is “he who is everywhere”
There is this story of Āndal which sums up this principle of all pervasiveness.
Āndal spent a night at a devotee’s house. When the lady of the house came to wake her up, she found Āndal sleeping with her feet pointing to the East or perhaps facing the puja room. She was shocked, but Āndal only replied thus “If I sleep with my feet facing East, he is of course there but if I sleep with my feet facing North or South is he not there? Shall I sleep standing on my head? But won’t my feet still be pointing towards him? Tell me what direction shall I point my feet in?
This is not to say that we must not follow the basic principles but just to illustrate the point of how “Viṣṇu” the name refers to “him who is everywhere…”
To put the pervasiveness of Vishnu in perspective – The earth is a speck in one of the distant outskirts of our galaxy called the Milky Way. The star that sustains us and the billion stars that populate this stretch are spread across a hundred thousand light years. If we were somehow to reach the edge of this galaxy and peer over the edge into the infinity of never-ending space, Viṣṇu would still be there and stretching even beyond…
Such is the nature of the person who is everywhere…