This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
跽 combines 足 (foot) with 忌, but the exact historical development is uncertain. It may relate to kneeling or a foot-related action, but no clear etymology is available.
The foot radical 足 beside 忌 suggests a foot-related action, but the exact meaning is unclear. Picture a foot hesitating or stopping in a cautious, avoidant way.
For キ, imagine a key (キー) that locks the foot in place, making it kneel: key -> キ, and the foot is fixed.