Vaiśravaṇa and Tamonten are two names for the same Buddhist deity. The Four Heavenly Kings guard the Buddha's teaching and the world from the four directions; Vaiśravaṇa presides over the north. In Japanese usage, the name Tamonten is common when he appears among the Four Kings, while Bishamonten is common when he is worshiped independently.
A deva, or ten in Japanese, is a divine protector of the Dharma. Vaiśravaṇa came to unite two powerful roles: guardian and giver of fortune. In Japan he was embraced as a protector of warriors and a bringer of prosperity, and eventually joined the Seven Gods of Good Fortune.
His Sanskrit name, Vaiśravaṇa, has been understood in the sense of "widely renowned" or "heard everywhere"; the Chinese name Duōwén, rendered Tamon in Japanese, preserves the element of hearing. In Indian tradition the name is also associated with Kubera, lord of wealth, from whom Vaiśravaṇa inherits his connection with treasure and abundance.