shine, shimmer, shining, dazzling
熒 centers on light that is bright and shimmering: shining, dazzling, or gleaming. The meanings all describe a vivid, eye-catching radiance.
熒 is thought to combine 火 (fire) with a phonetic element that also suggests brightness. The exact historical development of the upper component is uncertain.
The bottom is 火 (fire), and the top looks like a cluster of bright sparks or flames rising. Picture a fire that shimmers and dazzles with intense light.
For ケイ, imagine a bright, shimmering light shaped like the letter K: K -> ケイ, and the K-shaped glow shines dazzlingly.