afterglow; lingering light
Refers to the light that remains in the sky after sunset, or metaphorically to a fading remnant of something bright.
The afterglow of the sunset faded behind the mountain ridge.
A lingering light of hope still remained in his eyes.
Compound of 残 (ざん, 'remaining') and 光 (こう, 'light'). The exact historical derivation is uncertain, but the meaning is transparent from its components.