From his covering all creatures with illusion, from his being the support of the world and from his being of divine origin, he is know as Vasudeva. He is called Vishnu, owing to the fact of his pervading everything.
वसनात् सर्वभूतानां वसुत्वाद् देवयोनितः। वासुदेवस्ततो वेद्यो बृहत्त्वाद् विष्णुरुच्यते॥