shine
熈 centers on emitting light and radiance: to shine brightly. Its extended senses of joy, clarity, and spreading outward all grow from that core idea of brilliant illumination.
熈 is a variant form of 熙, which combines 灬 (fire) with a component that likely contributed the sound and the idea of brightness. The exact historical development of the upper part is uncertain.
The fire radical 灬 at the bottom provides the light. Above it, 臣 and 巳 together look like a bright, open face radiating joy. Picture a cheerful face glowing above a fire, spreading warmth and light.
For キ, imagine a key that unlocks a brilliant light: key -> キ, and turning the key makes the whole scene shine.