Ramayana
अरण्यां मथ्यामानायां प्रादुर्भूतो महातपाः । मथनान्मिथिरित्याहुर्जननाज्जनको ऽभवत् । यस्माद्विदेहात्सम्भूतो वैदेहस्तु ततः स्मृतः ॥ 7-57-19 ॥
As the kindling-stick was being churned, the one of great austerity came forth; because he arose from the churning (mathana) they called him Mithi, and because he was born (janana) he became Janaka; and because he was produced from a body-less one (Videha), he was thereafter remembered as Vaideha.
english translation