～光
～こう · ～kou · JLPT N1 · noun
light
💡 光 kou = light. 月光 gekkou = moon + light, 日光 nikkou = sun + light, 蛍光 keikou = firefly + light
As a suffix, 光 marks something that gives off light. Add it after a source word to name the light it makes, such as 月 (moon) becoming 月光 (moonlight).
光 — fire 火 (top) + person 儿 (bottom)
Originally a pictograph of a person with fire above their head, depicting a torchbearer or the radiance from a flame. The character evolved to mean 'light' or 'brightness' in general, and by extension 'glory' and 'to shine.' The modern top component is a stylized form of 火 (fire).