dotted cliff radical (no. 53)
广 is a radical that depicts a cliff with a dot, used as a building block in characters related to buildings, roofs, or shelter. Its standalone meaning is tied to this radical sense.
广 is a pictograph of a cliff with a dot, representing a shelter or building overhang. It serves as a semantic component in many characters related to dwellings.
The top horizontal stroke is the cliff edge, the left downward stroke is the cliff face, and the dot is a small cave or shelter beneath it. Picture a dotted cliff used as a roof.
For ゲン, imagine a gen (元) coin resting on the cliff's edge: gen -> ゲン, and the coin marks the dotted cliff.
—
kanji "dotted cliff" radical (radical 53)