light, clear, bright
囧 centers on light and clarity: something bright, clear, or illuminated. The given meanings all point to this same idea of visible radiance.
囧 is an ancient pictograph of a window or opening letting in light, with the outer 囗 representing the frame and the inner strokes suggesting the lattice or brightness shining through. The modern form preserves this window-like shape.
Picture an old window frame 囗 with light streaming through the crossed inner lines. The bright pattern inside makes the whole character glow: 囧 is light and clarity.
For ケイ, imagine a bright ray of light shaped like the letter K shining through the window: K -> ケイ, and the light makes everything clear.