sacrificial victim, gift, grain
餼 centers on offerings of food, especially grain, given as a gift or used in sacrifice. The meanings connect through the idea of providing sustenance as a ritual or generous act.
餼 combines the food radical 飠 with 氣, which likely provides the sound and may relate to the idea of vapor or spirit, suggesting food offered as a spiritual gift or sacrifice.
The food radical 飠 beside 氣 (which can suggest spirit or vapor) paints a picture of grain or food rising as an offering—a gift to the spirits or a sacrificial victim.
For キ, imagine a key-shaped loaf of grain bread given as a gift: key -> キ, and the key unlocks the idea of a sacrificial offering.