Vishnupurana 4.5.10

4.5.10

tatra ca kumāro jajñe jananāj janakasaṃjñāṃ cāvāpa ||

As Nimi left no successor, the Munis, apprehensive of the consequences of the earth being without a ruler, agitated the body of the prince, and produced from it a prince who was called Janaka, from being born without a progenitor. In consequence of his father being without a body (videha), he was termed also Vaideha, 'the son of the bodiless;' and the further received the name of Mithi, from having been produced by agitation (mathana). The son of Janaka was Udávasu;