Is is one of the eighteen Armanen runes, the runic row devised by the Austrian occultist Guido von List and published in his Das Geheimnis der Runen (The Secret of the Runes) in 1908, developing ideas he had begun to set out from about 1902. It is given the sound-value I.
The rune and its meaning
Von List did not recover an ancient alphabet. He built his eighteen runes on the sixteen characters of the Younger Futhark, expanded to eighteen to match the eighteen rune-charms of the Havamal in the Poetic Edda, and assigned to each a mystical meaning of his own. In his system Is stands for ice, the ego and the concentrated will; the doubt-free self, the power to hold firm through one's own certainty.
These readings are von List's early twentieth-century esoteric invention, not the meanings of the historical Viking-age runes, and are described here as such. The Armanen system was later taken up by volkisch and, in the 1930s and 1940s, National Socialist circles; that political appropriation is a separate and widely condemned chapter, and forms no part of the historical or comparative study of the row set out here.