Dharmaraja is the title of a Buddha, often mentioned in the Buddhist scriptures. For example, in the "Simile and Parable" (third) chapter of the Lotus Sutra

Lotus Sutra

The Lotus Sūtra is one of the most popular and influential Mahāyāna sūtras, and the basis on which the Tiantai and Nichiren sects of Buddhism were established.-Title:...

, Shakyamuni says, "I am the Dharma King, free to do as I will with the Dharma

Dharma

Dharma means Law or Natural Law and is a concept of central importance in Indian philosophy and religion. In the context of Hinduism, it refers to one's personal obligations, calling and duties, and a Hindu's dharma is affected by the person's age, caste, class, occupation, and gender...

. To bring peace and safety to living beings—that is the reason I appear in the world." Also, according to Mahayana Buddhism, each Buddha presides over his Pure Land

Pure land

A pure land, in Mahayana Buddhism, is the celestial realm or pure abode of a Buddha or Bodhisattva. The various traditions that focus on Pure Lands have been given the nomenclature Pure Land Buddhism. Pure lands are also evident in the literature and traditions of Taoism and Bön.The notion of 'pure...

, and hence this could explain the possible origin of the name Dharmaraja.