different, unusual, strange
异 centers on deviation from the norm: something different, unusual, or strange. The three given meanings are closely related facets of this single idea of not being ordinary.
异 is a character of uncertain origin. It visually combines 己 and 廾, but the historical relationship between these components and the meaning 'different' is not clearly established.
The top 己 (self) sits above two hands 廾, as if holding up one's own distinct identity. This self apart from others is what makes something different or strange.
For イ, imagine an eagle (イーグル) that looks unusual and different from other birds: the 'イ' from eagle cues the reading, while its strange appearance fits the meaning.