Isa (Proto-Germanic): ice; Eis (Gothic): ice;, Is (Old English): ice; Íss (Old Norse): ice
Phonetic value: ee as in "seed."
Esoteric meaning of name: primal matter/antimatter.
Ideographic interpretation: the icicle, or the primal ice stream/wave out of Niflheimer.
Isa is the polar opposite of Fehu. It is the world-ice that flows out of Niflheimr. It does not represent matter, but rather a concept of antimatter, which, when combined with the energy flowing from Muspellsheimr, leads to the formation of what we call "matter" (Midgard). Isa is similar to the prima material of other philosophies. In many ways an appropriate symbol for the mystery of this rune is the "black hole." This Rune is the force of attraction, gravity, inertia, entropy in the multiverse. In ice-giants (hrîmthursar). Isa isa a stillness and lack of vibration - a unique mystery in the cosmology of Germany. This idea is as metaphysical as that known as "spirit."
Ice and fire are the polar opposites that combine to create the world, but they are also the forces that will bring an end to "existence."
Isa represents the individual ego in that it's effects are centralized and concentrated. It is a force that holds the ego-self together during the stress of initiation trials, and as such it is a bridge between the worlds and over waters.