fortunate, auspicious
禧 centers on good fortune and favorable signs: something fortunate or auspicious. It expresses a state of blessing or happy omen.
禧 combines 示 (altar, spirit) with 喜 (joy, happiness), suggesting a joyful or fortunate spiritual event. The exact historical development is uncertain, but the component combination points to auspiciousness.
The left side 示 suggests a spiritual altar, and the right side 喜 means joy. Picture a joyful ceremony at an altar bringing good fortune and auspicious signs.
For キ, imagine a key unlocking a fortunate future: key -> キ, and the altar ceremony opens the door to auspicious events.