bright, clear, intelligent, light, brilliant, to understand, to illustrate
朙 centers on clarity and illumination: being bright, clear, or intelligent, and making things understood or illustrated. The meanings all flow from the idea of light making things visible and comprehensible.
朙 is an ancient form of 明, combining 囧 (a window or opening letting in light) with 月 (moon) to express brightness. The modern standard form 明 replaced 囧 with 日 (sun).
The left side 囧 looks like a window with light streaming through, and the right side 月 is the moon. Together they show a moonlit window, making everything bright and clear.
For メイ, picture a bright May moon shining through the window: May -> メイ, and the moonlight makes the room clear and understandable.