射す
さす · sasu · JLPT N3 · verb-godan
to shine
☀️🏹 射 = shoot, as in archery: sunlight shoots in like arrows
The kanji 射 means to shoot (射撃 = shooting). In 射す, light is what gets shot: 日が射す means the sun shines in. Sasu sounds like 刺す (to stab) and shares its sense of something piercing through.
射 — body 身 + inch/hand 寸
Originally a pictograph of a hand drawing a bow with an arrow. The ancient form showed 弓 (bow) plus 矢 (arrow) or a hand. Over time it was reshaped into 身 (body) plus 寸 (hand/measure), and the meaning 'to shoot' was extended to 'emit' or 'project'.