茵

Top grass radical — Kangxi #140 in its compressed three-stroke form. Supplies the meaning: 茵 originally named a chariot mat woven from soft grass, then any cushion or grassy underlay. The radical anchors 茵 in the botanical family alongside 草 grass, 苗 sprout, 莲 lotus.

Bottom 因 supplies the sound — yīn read straight across with no shift. A faint semantic echo rides along: 因 pictures a person 大 lying on a mat 囗, exactly the cushion-and-body image at the heart of 茵's original chariot-mat meaning. The two characters sometimes appeared interchangeably in classical texts before specializing.