The Self-God (in Shum, Emkaef) is a word my guru, Sivaya Subramuniyaswami, coined for the yogic spiritual enlightenment Nirvikalpa Samadhi. The Self-God (abbriviated as The Self in my guru's speak) is also the same as The Void or Sunya in Buddhist words. The origins of the word Self-God comes from a talk that Gurudeva gave to group of his devotees in San Francisco in 1959, that was later titled The Self God. Gurudeva explained that when he was giving this talk he was chanelling one of his spiritual guides, Rishi Kalidas. You can listen to this talk in its original recording at this link to Himalayan Academy's website by clicking here.
The Self God relates to the yoga philosophy that God can be discovered at the core of our being leading to the common proclamation by yogis and gurus that God and man are one. In meditative discovery God can be 'met' through various experiences such as witnessing His/Her form, feeling overwheming peace or contentment, experiencing blissful energy that pervades the universe or The Self God–simply God as Nothing. Of all the experiences of God, in Shum and almost all other traditional Eastern meditation practice the experience of The Self God is hailed as the ultimate goal.