rejoice, like, prefer, exclamation
憙 centers on a joyful, positive inclination: to rejoice, to like or prefer something, and to express that feeling as an exclamation.
憙 combines 喜 (joy, delight) with 心 (heart), reinforcing the idea of heartfelt joy or preference. The exact historical development is uncertain, but the component relationship is straightforward.
Joy 喜 rising from the heart 心: when your heart is full of joy, you rejoice, like things, and can't help but exclaim.
For キ, imagine a key that unlocks pure joy in your heart: key -> キ, and turning it makes you rejoice.