edge, margin, side, border
邊 centers on the outer limit or boundary of something: an edge, margin, side, or border.
邊 combines the movement radical 辶 with 臱, which likely contributes the sound and the idea of a boundary or edge. The exact historical development of 臱 is uncertain.
The movement radical 辶 suggests walking along the edge of something, while the inner part 臱 looks like a complex boundary marker. Together they mean edge or border.
For ヘン, imagine a hen pecking at the edge of a garden: hen -> ヘン, and the hen walks along the border.