This is the dvadashakshara, the twelve-syllable mantra, an invocation of Krishna addressed under the patronymic Vasudeva, son of Vasudeva. It is one of the central mantras of Vaishnavism, the devotional worship of Vishnu and his forms, recited as an act of surrender and remembrance and used in the repetitive practice of japa, the counting of the divine name on a rosary of beads. Beginning with the sacred syllable Om and the salutation namo (homage), it belongs to a family of Vaishnava mantras built on the form "homage to the Lord" followed by a name of the deity, and it is treated in the tradition as a means of turning the mind wholly toward Krishna. Its twelve syllables have themselves been the subject of devotional reflection, and it is transmitted within Vaishnava lineages as a mantra for regular repetition by devotees seeking refuge in the Lord.
The Bhagavata Purana, the text that gives this mantra its best-known setting in the story of the child devotee Dhruva, is generally dated by scholars to roughly the ninth or tenth century CE, centuries after the worship of Vasudeva itself, independently attested by the Besnagar pillar inscription of the second century BCE, evidence the deity and cult long predate the story that made their mantra popular. Dhruva's tale, a boy who undertakes severe ascetic practice after a slight at court and is rewarded with a vision of Vishnu, gave the mantra its lasting association with steadfastness, independent of its more technical role in temple consecration, where such namaskara mantras formally install and address the deity in the image itself.