instead, on the contrary, rather
卻 centers on a contrastive turn: instead of one thing, another; on the contrary; rather. It marks a shift away from an expected or previous state.
卻 combines 谷 (valley) and 卩 (a kneeling person or seal), but the historical origin of the compound is uncertain. It may have originally depicted a person retreating into a valley, suggesting a turning away or contrary movement, but this is speculative.
Imagine a person (卩) standing at the edge of a valley (谷) and deciding to turn back instead of crossing. That turning away captures the idea of 'instead' or 'on the contrary.'
For キャク, picture a person turning back from the valley with a sudden 'kyak!' sound of surprise—like a cartoon character doing a double-take. Kyak! -> キャク, and the person reverses course.