Apâm Napât (Zend). A mysterious being, corresponding to the Fohat of the Occultists. It is both a Vedic and an Avestian name. Literally, the name means the “Son of the Waters” (of space, i.e., Ether), for in the Avesta Apâm Napât stands between the fire-yazatas and the water-yazatas .(See Secret Doctrine, Vol. II., p. 400, note).
Source: H.P.Blavatsky - The Theosophical Glossary