thin, inferior
菲 centers on being thin or sparse, often with a sense of low quality or inferiority. The meanings describe something lacking substance or falling short of a standard.
菲 combines 艹 (grass/plant) with 非, which likely contributes the sound and the idea of being thin or sparse. The exact historical development is uncertain, but the plant component suggests something insubstantial or weedy.
The grass 艹 on top of 非 (which can suggest negation or scattering) looks like thin, sparse weeds that are inferior to healthy plants.
For ヒ, imagine a thin, inferior plant that barely reaches your knee: knee-high but weak -> ヒ.