movement of water, overflowing, billowing, wavy
灎 centers on water in dramatic motion: surging, overflowing, or forming large waves. The meanings all describe water that is not still but actively moving and rising.
灎 is a rare character combining 澧 (a water-related component) with 盍, which likely contributes a phonetic element. The exact historical development is uncertain, but the character is clearly built to express ideas of water movement.
The left side 澧 suggests water, and the right side 盍 looks like a container overflowing. Imagine a vessel so full that water spills out in billowing waves.
For エン, picture an enormous wave (エン sounds like 'N' in 'enormous') crashing and overflowing: enormous -> エン, and the wave is huge and wavy.