Ior is the sound io

Anglo-Saxon Rune Poem (from ragweedforge.com)
Ior is a river fish and yet it always feeds on land;
it has a fair abode encompassed by water, where it lives in happiness

Ior is a rune of boundaries and liminality. Liminality, from the word liminal, has a definition of being an intermediate state, phase, or transition. It is when you exist between two things. It is taken from the latin word for threshold. If you stand on the threshold of a door, you are liminal because you are neither inside nor outside, but intermediate, between those states. The river fish is a fish, but it feeds on land. It exists in a constant liminal state because it encompasses both of those features. Ior is speaking to that liminal state. You might be a liminal person yourself, or transitioning between two states, and are at an intermediate phase, where you are taking of both, but beholden to neither.